fuse: remove page alignment check for writeback len

Remove incorrect page alignment check for the writeback len arg in
fuse_iomap_writeback_range().  len will always be block-aligned as
passed in by iomap.

On regular fuse filesystems, i_blkbits is set to PAGE_SHIFT so this is
not a problem but for fuseblk filesystems, the block size is set to a
default of 512 bytes or a block size passed in at mount time.

Please note that non-page-aligned lengths are fine for the logic in
fuse_iomap_writeback_range().  The check was originally added as a
safeguard to detect conspicuously wrong ranges.

Signed-off-by: Joanne Koong <joannelkoong@gmail.com>
Fixes: ef7e7cbb ("fuse: use iomap for writeback")
Reported-by: Linux Kernel Functional Testing <lkft@linaro.org>
Link: https://lore.kernel.org/linux-fsdevel/CA+G9fYs5AdVM-T2Tf3LciNCwLZEHetcnSkHsjZajVwwpM2HmJw@mail.gmail.com/


Reported-by: Sasha Levin <sashal@kernel.org>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>