libceph: fix messenger CONFIG_BLOCK dependencies

The ceph messenger has a few spots that are only used when
bio messages are supported, and that's only when CONFIG_BLOCK
is defined.  This surrounds a couple of spots with #ifdef's
that would cause a problem if CONFIG_BLOCK were not present
in the kernel configuration.

This resolves:
    http://tracker.ceph.com/issues/3976

Signed-off-by: Alex Elder <elder@inktank.com>
Reviewed-by: Josh Durgin <josh.durgin@inktank.com>
diff --git a/net/ceph/messenger.c b/net/ceph/messenger.c
index 5ccf87e..8a62a55 100644
--- a/net/ceph/messenger.c
+++ b/net/ceph/messenger.c
@@ -9,8 +9,9 @@
 #include <linux/slab.h>
 #include <linux/socket.h>
 #include <linux/string.h>
+#ifdef	CONFIG_BLOCK
 #include <linux/bio.h>
-#include <linux/blkdev.h>
+#endif	/* CONFIG_BLOCK */
 #include <linux/dns_resolver.h>
 #include <net/tcp.h>
 
@@ -2651,9 +2652,11 @@
 	m->page_alignment = 0;
 	m->pages = NULL;
 	m->pagelist = NULL;
+#ifdef	CONFIG_BLOCK
 	m->bio = NULL;
 	m->bio_iter = NULL;
 	m->bio_seg = 0;
+#endif	/* CONFIG_BLOCK */
 	m->trail = NULL;
 
 	/* front */