net: bnx2x: convert to use get_rx_ring_count

net: bnx2x: convert to use get_rx_ring_count

Convert the bnx2x driver to use the new .get_rx_ring_count ethtool
operation instead of implementing .get_rxnfc solely for handling
ETHTOOL_GRXRINGS command. This simplifies the code by replacing the
switch statement with a direct return of the queue count.

The new callback provides the same functionality in a more direct way,
following the ongoing ethtool API modernization.

Signed-off-by: Breno Leitao <leitao@debian.org>
Reviewed-by: Simon Horman <horms@kernel.org>
Link: https://patch.msgid.link/20251112-bnx_grxrings-v1-1-1c2cb73979e2@debian.org
Signed-off-by: Jakub Kicinski <kuba@kernel.org>