ceph: make logical calculation functions return bool

This patch makes serverl logical caculation functions return bool to
improve readability due to these particular functions only using 0/1
as their return value.

No functional change.

Signed-off-by: Zhang Zhuoyu <zhangzhuoyu@cmss.chinamobile.com>
diff --git a/fs/ceph/cache.c b/fs/ceph/cache.c
index a351480..c052b5b 100644
--- a/fs/ceph/cache.c
+++ b/fs/ceph/cache.c
@@ -236,7 +236,7 @@
 	unlock_page(page);
 }
 
-static inline int cache_valid(struct ceph_inode_info *ci)
+static inline bool cache_valid(struct ceph_inode_info *ci)
 {
 	return ((ceph_caps_issued(ci) & CEPH_CAP_FILE_CACHE) &&
 		(ci->i_fscache_gen == ci->i_rdcache_gen));