cred: use 'const' in get_current_{user,groups}

Avoid annoying warnings from these functions ("discards qualifiers")
because they assign 'current_cred()' to a non-const pointer.
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

include/linux/cred.h

@@ -307,7 +307,7 @@ static inline void put_cred(const struct cred *_cred)
 #define get_current_user()				\
 ({							\
 	struct user_struct *__u;			\
-	struct cred *__cred;				\
+	const struct cred *__cred;			\
 	__cred = current_cred();			\
 	__u = get_uid(__cred->user);			\
 	__u;						\
@@ -322,7 +322,7 @@ static inline void put_cred(const struct cred *_cred)
 #define get_current_groups()				\
 ({							\
 	struct group_info *__groups;			\
-	struct cred *__cred;				\
+	const struct cred *__cred;			\
 	__cred = current_cred();			\
 	__groups = get_group_info(__cred->group_info);	\
 	__groups;					\