In rare conditions like two stage OS installation, the
ethtool's get_channels function may be called when the
device is in D3 state, leading to uncorrectable PCI error.
Check netif_running() first before making any query to FW
which involves writing to BAR.

Fixes: db4723b3 ("bnxt_en: Check max_tx_scheduler_inputs value from firmware.")
Signed-off-by: Pavan Chebbi <pavan.chebbi@broadcom.com>
Signed-off-by: Michael Chan <michael.chan@broadcom.com>
Signed-off-by: David S. Miller <davem@davemloft.net>