zram: remove bio parameter from zram_bvec_rw()

Recently rw_page block device operation has been added.  This patchset
implements rw_page operation for zram block device and does some clean-up.

This patch (of 3):

Remove an unnecessary parameter(bio) from zram_bvec_rw() and
zram_bvec_read().  zram_bvec_read() doesn't use a bio parameter, so remove
it.  zram_bvec_rw() calls a read/write operation not using bio, so a rw
parameter replaces a bio parameter.

Signed-off-by: karam.lee <karam.lee@lge.com>
Acked-by: Minchan Kim <minchan@kernel.org>
Acked-by: Jerome Marchand <jmarchan@redhat.com>
Cc: Matthew Wilcox <matthew.r.wilcox@intel.com>
Cc: Nitin Gupta <ngupta@vflare.org>
Cc: <seungho1.park@lge.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>