btrfs: fix direct I/O writes for split bios on zoned devices

btrfs: fix direct I/O writes for split bios on zoned devices

When a bio is split in btrfs_submit_direct, dip->file_offset contains
the file offset for the first bio.  But this means the start value used
in btrfs_end_dio_bio to record the write location for zone devices is
incorrect for subsequent bios.

CC: [email protected] # 5.16+
Reviewed-by: Johannes Thumshirn <[email protected]>
Reviewed-by: Naohiro Aota <[email protected]>
Reviewed-by: Qu Wenruo <[email protected]>
Reviewed-by: Sweet Tea Dorminy <[email protected]>
Signed-off-by: Christoph Hellwig <[email protected]>
Signed-off-by: David Sterba <[email protected]>