EX-8245 osc: use correct count

EX-8245 osc: use correct count

Using the number of bytes in the compressed page creates
gaps in the RDMA, which IB memory registration cannot
accept.

Fix this by always setting count to PAGE_SIZE for
compressed pages and otherwise using the count from the
original source page.  Setting PAGE_SIZE for compressed
pages is valid because client only does compression for
aligned IO, except for the trailing chunk.  For the
trailing chunk, the file size is set on the server, so any
trailing bytes are ignored.

Signed-off-by: Patrick Farrell <pfarrell@whamcloud.com>
Change-Id: Ied89d3ac328fb6020079392f5a8812ad5637b4a4
Reviewed-on: https://review.whamcloud.com/c/ex/lustre-release/+/52550
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>