ext4: Rename read_block_bitmap() to ext4_read_block_bitmap()

Since this a non-static function, make it be ext4 specific to avoid
conflicts with potentially other filesystems.

Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
diff --git a/fs/ext4/group.h b/fs/ext4/group.h
index 7eb0604..c2c0a8d 100644
--- a/fs/ext4/group.h
+++ b/fs/ext4/group.h
@@ -13,7 +13,7 @@
 				   struct ext4_group_desc *gdp);
 extern int ext4_group_desc_csum_verify(struct ext4_sb_info *sbi, __u32 group,
 				       struct ext4_group_desc *gdp);
-struct buffer_head *read_block_bitmap(struct super_block *sb,
+struct buffer_head *ext4_read_block_bitmap(struct super_block *sb,
 				      ext4_group_t block_group);
 extern unsigned ext4_init_block_bitmap(struct super_block *sb,
 				       struct buffer_head *bh,