staging: lustre: socklnd: simplify ksnc_rx_iov_space

ksnc_rx_iov_space is currently a union of two arrays,
one of 'struct kvec', the other of 'struct bio_vec'.

The 'struct bio_vec' option is never used.  The
array of kvec is used to read in a packet header, or
to read data that needs to be skipped so as to synchronize
with a packet boundary.
In each case the target memory location is a virtual address,
never a page, so 'struct bio_vec' is never needed.

When we read into a page, different code steps up a separate
array of 'struct bio_vec'.

So remove the bio_vec option, and remove the union ksock_rxiovspace..

Signed-off-by: NeilBrown <neilb@suse.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>