eth: fbnic: support an additional RSS context

Add support for an extra RSS context. The device has a primary
and a secondary context.

Signed-off-by: Daniel Zahka <daniel.zahka@gmail.com>
Reviewed-by: Joe Damato <jdamato@fastly.com>
Link: https://patch.msgid.link/20250206235334.1425329-4-kuba@kernel.org


Signed-off-by: Jakub Kicinski <kuba@kernel.org>