crypto: LLVMLinux: Remove VLAIS usage from libcrc32c.c

Replaced the use of a Variable Length Array In Struct (VLAIS) with a C99
compliant equivalent. This patch allocates the appropriate amount of memory
using a char array using the SHASH_DESC_ON_STACK macro.

The new code can be compiled with both gcc and clang.

Signed-off-by: Jan-Simon Möller <[e-mail]>
Signed-off-by: Behan Webster <[e-mail]>
Reviewed-by: Mark Charlebois <[e-mail]>
Acked-by: Herbert Xu <[e-mail]>
Cc: [e-mail]
Cc: "David S. Miller" <[e-mail]>

lib/libcrc32c.c

···
 
 u32 crc32c(u32 crc, const void *address, unsigned int length)
 {
-	struct {
-		struct shash_desc shash;
-		char ctx[crypto_shash_descsize(tfm)];
-	} desc;
+	SHASH_DESC_ON_STACK(shash, tfm);
+	u32 *ctx = (u32 *)shash_desc_ctx(shash);
 	int err;
 
-	desc.shash.tfm = tfm;
-	desc.shash.flags = 0;
-	*(u32 *)desc.ctx = crc;
+	shash->tfm = tfm;
+	shash->flags = 0;
+	*ctx = crc;
 
-	err = crypto_shash_update(&desc.shash, address, length);
+	err = crypto_shash_update(shash, address, length);
 	BUG_ON(err);
 
-	return *(u32 *)desc.ctx;
+	return *ctx;
 }
 
 EXPORT_SYMBOL(crc32c);