LU-13814 osc: convert osc_dio_submit to array

LU-13814 osc: convert osc_dio_submit to array

This is a trivial first step, converting from list to the
array of cl_pages, which is not a very useful step but
does have to be done as we proceed here.

Signed-off-by: Patrick Farrell <pfarrell@whamcloud.com>
Change-Id: Ib208bc2ed2ad95602a5fde79a4b39652ff73d9bf
Reviewed-on: https://review.whamcloud.com/c/fs/lustre-release/+/52159
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>
Reviewed-by: Marc Vef <mvef@whamcloud.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Tested-by: jenkins <devops@whamcloud.com>