Fix printk format warnings by using %zd for 'ssize_t' variables:

fs/ceph/file.c:751:2: warning: format '%ld' expects argument of type 'long int', but argument 11 has type 'ssize_t' [-Wformat]
fs/ceph/file.c:762:2: warning: format '%ld' expects argument of type 'long int', but argument 11 has type 'ssize_t' [-Wformat]
Signed-off-by: NRandy Dunlap <rdunlap@infradead.org>
Cc:	ceph-devel@vger.kernel.org
Signed-off-by: NSage Weil <sage@inktank.com>