eth: bnxt: store rx buffer size per queue

eth: bnxt: store rx buffer size per queue

Instead of using a constant buffer length, allow configuring the size
for each queue separately. There is no way to change the length yet, and
it'll be passed from memory providers in a later patch.

Suggested-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>