sha2.c: Changed address calculation to avoid type punning.

Use pointer arithmetics instead of taking the address of a
dereferenced array value to quiet warning about type punned pointer.

Change-Id: I6c833dafbf26502c8b4d132f21a733cc4f133bdb

sha2/sha2.c

diff --git a/sha2/sha2.c b/sha2/sha2.c
index c5e45b3..5f55352 100644
--- a/sha2/sha2.c
+++ b/sha2/sha2.c
@@ -637,7 +637,7 @@
 			*context->buffer = 0x80;
 		}
 		/* Set the bit count: */
-		*(sha2_word64*)&context->buffer[DTLS_SHA256_SHORT_BLOCK_LENGTH] = context->bitcount;
+                *(sha2_word64*)(context->buffer+DTLS_SHA256_SHORT_BLOCK_LENGTH) = context->bitcount;
 
 		/* Final transform: */
 		dtls_sha256_transform(context, (sha2_word32*)context->buffer);