ore: Remove support of partial IO request (NFS crash)

ore: Remove support of partial IO request (NFS crash)

commit 62b62ad873f2accad9222a4d7ffbe1e93f6714c1 upstream.

Do to OOM situations the ore might fail to allocate all resources
needed for IO of the full request. If some progress was possible
it would proceed with a partial/short request, for the sake of
forward progress.

Since this crashes NFS-core and exofs is just fine without it just
remove this contraption, and fail.

TODO:
	Support real forward progress with some reserved allocations
	of resources, such as mem pools and/or bio_sets

[Bug since 3.2 Kernel]
CC: Benny Halevy <bhalevy@tonian.com>
Signed-off-by: Boaz Harrosh <bharrosh@panasas.com>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>