[GFS2] Rename get_block and make it extern

This renames get_block to gfs2_get_block and makes it accessible
from outside ops_address.c.

Signed-off-by: Steven Whitehouse <swhiteho@redhat.com>
diff --git a/fs/gfs2/ops_address.h b/fs/gfs2/ops_address.h
index ced9ea0..f201a05 100644
--- a/fs/gfs2/ops_address.h
+++ b/fs/gfs2/ops_address.h
@@ -11,5 +11,7 @@
 #define __OPS_ADDRESS_DOT_H__
 
 extern struct address_space_operations gfs2_file_aops;
+extern int gfs2_get_block(struct inode *inode, sector_t lblock,
+			  struct buffer_head *bh_result, int create);
 
 #endif /* __OPS_ADDRESS_DOT_H__ */