xfs: Remove redundant assignment of mp

mp is being initialized to log->l_mp but this is never read
as record is overwritten later on. Remove the redundant
assignment.

Cleans up the following clang-analyzer warning:

fs/xfs/xfs_log_recover.c:3543:20: warning: Value stored to 'mp' during
its initialization is never read [clang-analyzer-deadcode.DeadStores].
Reported-by: Abaci Robot <abaci@linux.alibaba.com>
Signed-off-by: Jiapeng Chong <jiapeng.chong@linux.alibaba.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Signed-off-by: Darrick J. Wong <djwong@kernel.org>

fs/xfs/xfs_log_recover.c

@@ -3550,8 +3550,6 @@ xlog_recover_check_summary(
 	uint64_t		ifree;
 	int			error;
 
-	mp = log->l_mp;
-
 	freeblks = 0LL;
 	itotal = 0LL;
 	ifree = 0LL;