EX-7601 ofd: add ofd_decompress_read implementation

EX-7601 ofd: add ofd_decompress_read implementation

ofd_decompress_read is responsible for walking the
remote niobufs (rnbs) in the RPC and identifying if they
are chunk unaligned.  It then passes them on to the rnb
decompression code (not implemented yet, see next patch).

It also allocates the bounce buffers for decompression so
they can be reused for each remote niobuf.

Signed-off-by: Patrick Farrell <pfarrell@whamcloud.com>
Change-Id: I1f2f86ce3fc036ac5d79b060a5e44f6564e123aa
Reviewed-on: https://review.whamcloud.com/c/ex/lustre-release/+/52868
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>