bnxt_en: Resize RSS contexts on channel count change

bnxt_en: Resize RSS contexts on channel count change

bnxt_set_channels() previously rejected channel changes that alter the
RSS table size when RSS contexts exist, because non-default context
sizes were locked at creation.

Replace the rejection with the new resize helpers.

RSS table size only changes on P5 chips with older firmware; newer
firmware always uses the largest table size.

Signed-off-by: Björn Töpel <bjorn@kernel.org>
Link: https://patch.msgid.link/20260320085826.1957255-4-bjorn@kernel.org
Signed-off-by: Jakub Kicinski <kuba@kernel.org>