EX-7601 ofd: add remote_pages

EX-7601 ofd: add remote_pages

When we round a read to get all of the compressed chunks,
the number of local and the number of remote pages will
differ.  We need to make sure we do the checksum and data
transfer using the number of remote pages, not the number of
local pages.

This patch calculates the number of remote pages and uses it
accordingly.  This doesn't do anything yet, but when we
round the local read to include the whole compressed chunk,
this will be needed.

Signed-off-by: Patrick Farrell <pfarrell@whamcloud.com>
Change-Id: I4875b02016570d227b3b926efd117f0a7cda41b4
Reviewed-on: https://review.whamcloud.com/c/ex/lustre-release/+/52878
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Artem Blagodarenko <ablagodarenko@ddn.com>
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>