[XFS] Fix up sparse warnings.

These are mostly locking annotations, marking things static, casts where
needed and declaring stuff in header files.

SGI-PV: 971186
SGI-Modid: xfs-linux-melb:xfs-kern:30002a

Signed-off-by: David Chinner <dgc@sgi.com>
Signed-off-by: Christoph Hellwig <hch@infradead.org>
Signed-off-by: Lachlan McIlroy <lachlan@sgi.com>

fs/xfs/linux-2.6/xfs_globals.c

@@ -47,5 +47,6 @@ xfs_param_t xfs_params = {
 /*
  * Global system credential structure.
  */
-cred_t sys_cred_val, *sys_cred = &sys_cred_val;
+static cred_t sys_cred_val;
+cred_t *sys_cred = &sys_cred_val;