bnxt_en: Skip ethtool RSS context configuration in ifdown state

bnxt_en: Skip ethtool RSS context configuration in ifdown state

The current implementation requires the ifstate to be up when
configuring the RSS contexts.  It will try to fetch the RX ring
IDs and will crash if it is in ifdown state.  Return error if
!netif_running() to prevent the crash.

An improved implementation is in the works to allow RSS contexts
to be changed while in ifdown state.

Fixes: b3d0083caf9a ("bnxt_en: Support RSS contexts in ethtool .{get|set}_rxfh()")
Reviewed-by: Kalesh AP <kalesh-anakkur.purayil@broadcom.com>
Reviewed-by: Somnath Kotur <somnath.kotur@broadcom.com>
Signed-off-by: Pavan Chebbi <pavan.chebbi@broadcom.com>
Signed-off-by: Michael Chan <michael.chan@broadcom.com>
Reviewed-by: Jacob Keller <jacob.e.keller@intel.com>
Link: https://lore.kernel.org/r/20240409215431.41424-2-michael.chan@broadcom.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>