LU-13004 modules: replace lnet_kiov_t with struct bio_vec

LU-13004 modules: replace lnet_kiov_t with struct bio_vec

lnet_kiov_t has the same structure and general purpose
as struct bio_vec - only the names a different.
The difference brings no value - so let's remove it.
sed -e 's/lnet_kiov_t/struct biovec/g'
    -e 's/kiov_page/bv_page/g'
    -e 's/kiov_len/bv_len/g'
    -e 's/kiov_offset/bv_offset/g'

plus some cleaning up.

Test-Parameters: trivial
Signed-off-by: Mr NeilBrown <neilb@suse.de>
Change-Id: Ia718e5880d0fbbb9aa9aed0edf48a2b2c42b54d3
Reviewed-on: https://review.whamcloud.com/37852
Reviewed-by: James Simmons <jsimmons@infradead.org>
Reviewed-by: Shaun Tancheff <shaun.tancheff@hpe.com>
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>