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/gcm.c b/library/gcm.c
index bccecc0..948268c 100644
--- a/library/gcm.c
+++ b/library/gcm.c
@@ -88,12 +88,12 @@
         return( ret );
 
     /* pack h as two 64-bits ints, big-endian */
-    MBEDTLS_GET_UINT32_BE( hi, h,  0  );
-    MBEDTLS_GET_UINT32_BE( lo, h,  4  );
+    hi = MBEDTLS_GET_UINT32_BE( h,  0  );
+    lo = MBEDTLS_GET_UINT32_BE( h,  4  );
     vh = (uint64_t) hi << 32 | lo;
 
-    MBEDTLS_GET_UINT32_BE( hi, h,  8  );
-    MBEDTLS_GET_UINT32_BE( lo, h,  12 );
+    hi = MBEDTLS_GET_UINT32_BE( h,  8  );
+    lo = MBEDTLS_GET_UINT32_BE( h,  12 );
     vl = (uint64_t) hi << 32 | lo;
 
     /* 8 = 1000 corresponds to 1 in GF(2^128) */