bnxt_en: Reserve rings after PCIe AER recovery if NIC interface is down

After successful PCIe AER recovery, FW will reset all resource
reservations.  If it is IF_UP, the driver will call bnxt_open() and
all resources will be reserved again.  It it is IF_DOWN, we should
call bnxt_reserve_rings() so that we can reserve resources including
RoCE resources to allow RoCE to resume after AER.  Without this
patch, RoCE fails to resume in this IF_DOWN scenario.

Later, if it becomes IF_UP, bnxt_open() will see that resources have
been reserved and will not reserve again.

Fixes: fb1e6e56 ("bnxt_en: Fix AER recovery.")
Reviewed-by: Somnath Kotur <somnath.kotur@broadcom.com>
Reviewed-by: Pavan Chebbi <pavan.chebbi@broadcom.com>
Reviewed-by: Kashyap Desai <kashyap.desai@broadcom.com>
Signed-off-by: Saravanan Vajravel <saravanan.vajravel@broadcom.com>
Signed-off-by: Michael Chan <michael.chan@broadcom.com>
Signed-off-by: Paolo Abeni <pabeni@redhat.com>