Remove inline workaround when not useful

This header doesn't have nay inline function any more
diff --git a/include/mbedtls/md.h b/include/mbedtls/md.h
index a70d7a6..77c2c6f 100644
--- a/include/mbedtls/md.h
+++ b/include/mbedtls/md.h
@@ -27,11 +27,6 @@
 
 #include <stddef.h>
 
-#if ( defined(__ARMCC_VERSION) || defined(_MSC_VER) ) && \
-    !defined(inline) && !defined(__cplusplus)
-#define inline __inline
-#endif
-
 #define MBEDTLS_ERR_MD_FEATURE_UNAVAILABLE                -0x5080  /**< The selected feature is not available. */
 #define MBEDTLS_ERR_MD_BAD_INPUT_DATA                     -0x5100  /**< Bad input parameters to function. */
 #define MBEDTLS_ERR_MD_ALLOC_FAILED                       -0x5180  /**< Failed to allocate memory. */