staging: skein: fixed sparse warnings related to static declarations

drivers/staging/skein/skein_generic.c:30:5: warning: symbol 'skein256_update' was not declared. Should it be static?
drivers/staging/skein/skein_generic.c:65:5: warning: symbol 'skein512_update' was not declared. Should it be static?
drivers/staging/skein/skein_generic.c:100:5: warning: symbol 'skein1024_update' was not declared. Should it be static?
Signed-off-by: Niklas Svensson <nks@flawful.org>
Acked-by: Jason Cooper <jason@lakedaemon.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/skein/skein_generic.c

@@ -27,7 +27,7 @@ static int skein256_init(struct shash_desc *desc)
 			SKEIN256_DIGEST_BIT_SIZE);
 }
 
-int skein256_update(struct shash_desc *desc, const u8 *data,
+static int skein256_update(struct shash_desc *desc, const u8 *data,
 			unsigned int len)
 {
 	return skein_256_update((struct skein_256_ctx *)shash_desc_ctx(desc),
@@ -62,7 +62,7 @@ static int skein512_init(struct shash_desc *desc)
 				SKEIN512_DIGEST_BIT_SIZE);
 }
 
-int skein512_update(struct shash_desc *desc, const u8 *data,
+static int skein512_update(struct shash_desc *desc, const u8 *data,
 			unsigned int len)
 {
 	return skein_512_update((struct skein_512_ctx *)shash_desc_ctx(desc),
@@ -97,7 +97,7 @@ static int skein1024_init(struct shash_desc *desc)
 				SKEIN1024_DIGEST_BIT_SIZE);
 }
 
-int skein1024_update(struct shash_desc *desc, const u8 *data,
+static int skein1024_update(struct shash_desc *desc, const u8 *data,
 			unsigned int len)
 {
 	return skein_1024_update((struct skein_1024_ctx *)shash_desc_ctx(desc),