lib: digital signature config option name change

It was reported that DIGSIG is confusing name for digital signature
module. It was suggested to rename DIGSIG to SIGNATURE.

Requested-by: Linus Torvalds <torvalds@linux-foundation.org>
Suggested-by: Pavel Machek <pavel@ucw.cz>
Signed-off-by: Dmitry Kasatkin <dmitry.kasatkin@intel.com>
Signed-off-by: James Morris <jmorris@namei.org>
diff --git a/include/linux/digsig.h b/include/linux/digsig.h
index efae755..b01558b 100644
--- a/include/linux/digsig.h
+++ b/include/linux/digsig.h
@@ -46,7 +46,7 @@
 	char		mpi[0];
 } __packed;
 
-#if defined(CONFIG_DIGSIG) || defined(CONFIG_DIGSIG_MODULE)
+#if defined(CONFIG_SIGNATURE) || defined(CONFIG_SIGNATURE_MODULE)
 
 int digsig_verify(struct key *keyring, const char *sig, int siglen,
 					const char *digest, int digestlen);
@@ -59,6 +59,6 @@
 	return -EOPNOTSUPP;
 }
 
-#endif /* CONFIG_DIGSIG */
+#endif /* CONFIG_SIGNATURE */
 
 #endif /* _DIGSIG_H */