xfs: compact deferred intent item structures

mainline inclusion
from mainline-v5.15-rc4
commit 9e253954
category: bugfix
bugzilla: 188883, https://gitee.com/openeuler/kernel/issues/I76JSK
CVE: NA

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=9e253954acf53227f33d307f5ac5ff94c1ca5880



--------------------------------

Rearrange these structs to reduce the amount of unused padding bytes.
This saves eight bytes for each of the three structs changed here, which
means they're now all (rmap/bmap are 64 bytes, refc is 32 bytes) even
powers of two.

Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Chandan Babu R <chandan.babu@oracle.com>
Signed-off-by: Long Li <leo.lilong@huawei.com>