GET macros use a target variable

The GET macros used to write to a macro parameter, but now
they can be used to assign a value to the desired variable
rather than pass it in as an argument and have it modified
in the macro function.

Due to this MBEDTLS_BYTES_TO_U32_LE is the same as
MBEDTLS_GET_UINT32_LE and was there for replaced in the
appropriate files and removed from common.h

Signed-off-by: Joe Subbiani <joe.subbiani@arm.com>
diff --git a/library/nist_kw.c b/library/nist_kw.c
index b8f9239..e2ab256 100644
--- a/library/nist_kw.c
+++ b/library/nist_kw.c
@@ -454,7 +454,7 @@
             ret = MBEDTLS_ERR_CIPHER_AUTH_FAILED;
         }
 
-        MBEDTLS_GET_UINT32_BE( Plen, A, KW_SEMIBLOCK_LENGTH / 2 );
+        Plen = MBEDTLS_GET_UINT32_BE( A, KW_SEMIBLOCK_LENGTH / 2 );
 
         /*
          * Plen is the length of the plaintext, when the input is valid.