reiserfs: Remove unneed check in reiserfs_write_full_page()

Condition !A || A && B is equivalent to !A || B.

Generated by: scripts/coccinelle/misc/excluded_middle.cocci

Link: https://lore.kernel.org/r/20210523090258.27696-1-yuehaibing@huawei.com
Signed-off-by: YueHaibing <yuehaibing@huawei.com>
Signed-off-by: Jan Kara <jack@suse.cz>