ext4: remove the unused EXT4_CURRENT_REV macro

There are no callers of the EXT4_CURRENT_REV macro, so remove it.
Signed-off-by: Kaixu Xia <kaixuxia@tencent.com>
Reviewed-by: Jan Kara <jack@suse.cz>
Link: https://lore.kernel.org/r/1605164202-31120-1-git-send-email-kaixuxia@tencent.comSigned-off-by: Theodore Ts'o <tytso@mit.edu>

fs/ext4/ext4.h

@@ -1868,7 +1868,6 @@ static inline bool ext4_verity_in_progress(struct inode *inode)
 #define EXT4_GOOD_OLD_REV	0	/* The good old (original) format */
 #define EXT4_DYNAMIC_REV	1	/* V2 format w/ dynamic inode sizes */
 
-#define EXT4_CURRENT_REV	EXT4_GOOD_OLD_REV
 #define EXT4_MAX_SUPP_REV	EXT4_DYNAMIC_REV
 
 #define EXT4_GOOD_OLD_INODE_SIZE 128