xfs: convert XFS_IFORK_PTR to a static inline helper

mainline inclusion
from mainline-v5.19-rc5
commit 732436ef
category: bugfix
bugzilla: 187164, https://gitee.com/openeuler/kernel/issues/I4KIAO
CVE: NA

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=732436ef916b4f338d672ea56accfdb11e8d0732



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

We're about to make this logic do a bit more, so convert the macro to a
static inline function for better typechecking and fewer shouty macros.
No functional changes here.

Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Dave Chinner <dchinner@redhat.com>

conflicts:
	fs/xfs/libxfs/xfs_bmap.c
	fs/xfs/libxfs/xfs_bmap_btree.c
	fs/xfs/libxfs/xfs_inode_fork.c
	fs/xfs/libxfs/xfs_inode_fork.h
	fs/xfs/scrub/bmap.c
	fs/xfs/scrub/symlink.c
	fs/xfs/xfs_inode.c
	fs/xfs/xfs_ioctl.c
	fs/xfs/xfs_qm.c
	fs/xfs/xfs_reflink.c

Signed-off-by: Long Li <leo.lilong@huawei.com>
Reviewed-by: Zhang Yi <yi.zhang@huawei.com>
Signed-off-by: Jialin Zhang <zhangjialin11@huawei.com>