userns: Convert loop to use kuid_t instead of uid_t

Cc: Jens Axboe <jaxboe@fusionio.com>
Acked-by: Serge Hallyn <serge.hallyn@canonical.com>
Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>

init/Kconfig

@@ -960,7 +960,6 @@ config UIDGID_CONVERTED
 	depends on !UML || HOSTFS = n
 
 	# The rare drivers that won't build
-	depends on BLK_DEV_LOOP = n
 	depends on ANDROID_BINDER_IPC = n
 
 	# Security modules