f2fs: do not allow partial truncation on pinned file

[ Upstream commit 5fed0be8 ]

If the pinned file has a hole by partial truncation, application that has
the block map will be broken.

Reviewed-by: Chao Yu <chao@kernel.org>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
Stable-dep-of: 278a6253 ("f2fs: fix to relocate check condition in f2fs_fallocate()")
Signed-off-by: Sasha Levin <sashal@kernel.org>