f2fs: decrease spare area for pinned files for zoned devices

[ Upstream commit fa08972b ]

Now we reclaim too much space before allocating pinned space for zoned
devices.

Signed-off-by: Daeho Jeong <daehojeong@google.com>
Reviewed-by: Chao Yu <chao@kernel.org>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
Stable-dep-of: dc6d9ef5 ("f2fs: zone: fix to calculate first_zoned_segno correctly")
Signed-off-by: Sasha Levin <sashal@kernel.org>