staging: qlge: Update buffer queue prod index despite oom

Currently, if we repeatedly fail to allocate all of the buffers from the
desired batching budget, we will never update the prod_idx register.
Restructure code to always update prod_idx if new buffers could be
allocated. This eliminates the current two stage process (clean_idx ->
prod_idx) and some associated bookkeeping variables.

Signed-off-by: Benjamin Poirier <bpoirier@suse.com>
Link: https://lore.kernel.org/r/20190927101210.23856-16-bpoirier@suse.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>