xfs: Make the symbol 'xfs_rtalloc_log_count' static

Fix the following sparse warning:

fs/xfs/libxfs/xfs_trans_resv.c:206:1: warning: symbol 'xfs_rtalloc_log_count' was not declared. Should it be static?

Fixes: b1de6fc752 ("xfs: fix log reservation overflows when allocating large rt extents")
Signed-off-by: Chen Wandun <chenwandun@huawei.com>
Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>

fs/xfs/libxfs/xfs_trans_resv.c

@@ -202,7 +202,7 @@ xfs_calc_inode_chunk_res(
  * blocks as needed to mark inuse MAXEXTLEN blocks' worth of realtime extents,
  * as well as the realtime summary block.
  */
-unsigned int
+static unsigned int
 xfs_rtalloc_log_count(
 	struct xfs_mount	*mp,
 	unsigned int		num_ops)