crypto: sha256 - Add missing MODULE_LICENSE() to lib/crypto/sha256.c

lib/crypto/sha256.c / lib/crypto/libsha256.o may end up being a module,
so it needs a MODULE_LICENSE() line, add this.
Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>

lib/crypto/sha256.c

@@ -13,6 +13,7 @@
 
 #include <linux/bitops.h>
 #include <linux/export.h>
+#include <linux/module.h>
 #include <linux/string.h>
 #include <crypto/sha256.h>
 #include <asm/unaligned.h>
@@ -314,3 +315,5 @@ int sha224_final(struct sha256_state *sctx, u8 *out)
 	return __sha256_final(sctx, out, 7);
 }
 EXPORT_SYMBOL(sha224_final);
+
+MODULE_LICENSE("GPL");