Move MBEDTLS_ERR_xxx Doxygen comments before the definition

Now that descriptions of error codes no longer have to be on the same line
for the sake of generate_errors.pl, move them to their own line before the
definition. This aligns them with what we do for other definitions, and
means that we no longer need to have very long lines containing both the C
definition and the comment.

```
perl -i -pe 's~^(#define +MBEDTLS_ERR_\w+ +-\w+) */\*[*!]<(.*)\*/~/**$2*/\n$1~' include/mbedtls/*.h
```

This commit does not change the output of generate_errors.pl.

Signed-off-by: Gilles Peskine <Gilles.Peskine@arm.com>
diff --git a/include/mbedtls/dhm.h b/include/mbedtls/dhm.h
index c7830b9..c4b15a2 100644
--- a/include/mbedtls/dhm.h
+++ b/include/mbedtls/dhm.h
@@ -73,20 +73,31 @@
 /*
  * DHM Error codes
  */
-#define MBEDTLS_ERR_DHM_BAD_INPUT_DATA                    -0x3080  /**< Bad input parameters. */
-#define MBEDTLS_ERR_DHM_READ_PARAMS_FAILED                -0x3100  /**< Reading of the DHM parameters failed. */
-#define MBEDTLS_ERR_DHM_MAKE_PARAMS_FAILED                -0x3180  /**< Making of the DHM parameters failed. */
-#define MBEDTLS_ERR_DHM_READ_PUBLIC_FAILED                -0x3200  /**< Reading of the public values failed. */
-#define MBEDTLS_ERR_DHM_MAKE_PUBLIC_FAILED                -0x3280  /**< Making of the public value failed. */
-#define MBEDTLS_ERR_DHM_CALC_SECRET_FAILED                -0x3300  /**< Calculation of the DHM secret failed. */
-#define MBEDTLS_ERR_DHM_INVALID_FORMAT                    -0x3380  /**< The ASN.1 data is not formatted correctly. */
-#define MBEDTLS_ERR_DHM_ALLOC_FAILED                      -0x3400  /**< Allocation of memory failed. */
-#define MBEDTLS_ERR_DHM_FILE_IO_ERROR                     -0x3480  /**< Read or write of file failed. */
+/** Bad input parameters. */
+#define MBEDTLS_ERR_DHM_BAD_INPUT_DATA                    -0x3080
+/** Reading of the DHM parameters failed. */
+#define MBEDTLS_ERR_DHM_READ_PARAMS_FAILED                -0x3100
+/** Making of the DHM parameters failed. */
+#define MBEDTLS_ERR_DHM_MAKE_PARAMS_FAILED                -0x3180
+/** Reading of the public values failed. */
+#define MBEDTLS_ERR_DHM_READ_PUBLIC_FAILED                -0x3200
+/** Making of the public value failed. */
+#define MBEDTLS_ERR_DHM_MAKE_PUBLIC_FAILED                -0x3280
+/** Calculation of the DHM secret failed. */
+#define MBEDTLS_ERR_DHM_CALC_SECRET_FAILED                -0x3300
+/** The ASN.1 data is not formatted correctly. */
+#define MBEDTLS_ERR_DHM_INVALID_FORMAT                    -0x3380
+/** Allocation of memory failed. */
+#define MBEDTLS_ERR_DHM_ALLOC_FAILED                      -0x3400
+/** Read or write of file failed. */
+#define MBEDTLS_ERR_DHM_FILE_IO_ERROR                     -0x3480
 
 /* MBEDTLS_ERR_DHM_HW_ACCEL_FAILED is deprecated and should not be used. */
-#define MBEDTLS_ERR_DHM_HW_ACCEL_FAILED                   -0x3500  /**< DHM hardware accelerator failed. */
+/** DHM hardware accelerator failed. */
+#define MBEDTLS_ERR_DHM_HW_ACCEL_FAILED                   -0x3500
 
-#define MBEDTLS_ERR_DHM_SET_GROUP_FAILED                  -0x3580  /**< Setting the modulus and generator failed. */
+/** Setting the modulus and generator failed. */
+#define MBEDTLS_ERR_DHM_SET_GROUP_FAILED                  -0x3580
 
 #ifdef __cplusplus
 extern "C" {