[GFS2] Spelling sentinal -> sentinel

A spelling mistake (one of mine).

Cc: Jan Engelhardt <jengelh@linux01.gwdg.de>
Signed-off-by: Steven Whitehouse <swhiteho@redhat.com>
diff --git a/fs/gfs2/ops_file.h b/fs/gfs2/ops_file.h
index 064e52c..b1c1bf8 100644
--- a/fs/gfs2/ops_file.h
+++ b/fs/gfs2/ops_file.h
@@ -9,7 +9,7 @@
 
 #ifndef __OPS_FILE_DOT_H__
 #define __OPS_FILE_DOT_H__
-extern struct file gfs2_internal_file_sentinal;
+extern struct file gfs2_internal_file_sentinel;
 extern int gfs2_internal_read(struct gfs2_inode *ip,
 			      struct file_ra_state *ra_state,
 			      char *buf, loff_t *pos, unsigned size);