userns: Silence silly gcc warning.

On 32bit builds gcc says:
kernel/user.c:30:4: warning: this decimal constant is unsigned only in ISO C90 [enabled by default]
kernel/user.c:38:4: warning: this decimal constant is unsigned only in ISO C90 [enabled by default]

Silence gcc by changing the constant 4294967295 to 4294967295U.

Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>

kernel/user.c

@@ -27,15 +27,15 @@ struct user_namespace init_user_ns = {
 		.extent[0] = {
 			.first = 0,
 			.lower_first = 0,
-			.count = 4294967295,
+			.count = 4294967295U,
 		},
 	},
 	.gid_map = {
 		.nr_extents = 1,
 		.extent[0] = {
 			.first = 0,
 			.lower_first = 0,
-			.count = 4294967295,
+			.count = 4294967295U,
 		},
 	},
 	.kref = {