BACKPORT: f2fs: invalidate meta pages only for post_read required inode

After commit e3b49ea3 ("f2fs: invalidate META_MAPPING before
IPU/DIO write"), invalidate_mapping_pages() will be called to
avoid race condition in between IPU/DIO and readahead for GC.

However, readahead flow is only used for post_read required inode,
so this patch adds check condition to avoids unnecessary page cache
invalidating for non-post_read inode.

Bug: 243874214
Bug: 244749885

Signed-off-by: Chao Yu <chao.yu@oppo.com>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
Signed-off-by: Chao Yu <chao@kernel.org>
(cherry picked from commit 0d5b9d81)
Change-Id: I39a8da4183b59b34522f445d25d8ab9fd2d6319c
(cherry picked from commit 22b447e9)