Allow SHA-512 unaligned data access in |OPENSSL_NO_ASM| mode.

The previous logic only defined
|SHA512_BLOCK_CAN_MANAGE_UNALIGNED_DATA| when the assembly language
optimizations were enabled, but
|SHA512_BLOCK_CAN_MANAGE_UNALIGNED_DATA| is also useful when the C
implementations are used.

If support for ARM processors that don't support unaligned access is
important, then it might be better to condition the enabling of
|SHA512_BLOCK_CAN_MANAGE_UNALIGNED_DATA| on ARM based on more specific
flags.

Change-Id: Ie8c37c73aba308c3ccf79371ce5831512e419989
Reviewed-on: https://boringssl-review.googlesource.com/6402
Reviewed-by: Adam Langley <agl@google.com>

crypto/sha/sha512.c

@@ -78,10 +78,14 @@
 #if !defined(OPENSSL_NO_ASM) &&                         \
     (defined(OPENSSL_X86) || defined(OPENSSL_X86_64) || \
      defined(OPENSSL_ARM) || defined(OPENSSL_AARCH64))
-#define SHA512_BLOCK_CAN_MANAGE_UNALIGNED_DATA
 #define SHA512_ASM
 #endif
 
+#if defined(OPENSSL_X86) || defined(OPENSSL_X86_64) || \
+    defined(__ARM_FEATURE_UNALIGNED)
+#define SHA512_BLOCK_CAN_MANAGE_UNALIGNED_DATA
+#endif
+
 int SHA384_Init(SHA512_CTX *sha) {
   sha->h[0] = OPENSSL_U64(0xcbbb9d5dc1059ed8);
   sha->h[1] = OPENSSL_U64(0x629a292a367cd507);