bnxt: convert to core rx_mode retry mechanism

bnxt: convert to core rx_mode retry mechanism

Remove the driver-specific BNXT_STATE_L2_FILTER_RETRY + timer + sp_task
retry mechanism and rely on the core stack's ndo_set_rx_mode_async retry
instead.

bnxt_cfg_rx_mode() now returns errors instead of swallowing them. The
PF-unavailable case (-ENODEV from HWRM on a VF) is normalized to
-EAGAIN at the boundary so callers can match on a single "retry me"
errno without re-implementing the VF/-ENODEV check. Other errors
propagate unchanged.

This removes:
- BNXT_STATE_L2_FILTER_RETRY state bit
- BNXT_RX_MASK_SP_EVENT sp_event bit
- Retry trigger from bnxt_timer()
- BNXT_RX_MASK_SP_EVENT handling from bnxt_sp_task()

bnxt_init_chip() still calls bnxt_cfg_rx_mode() directly during open.
On a fresh open dev->uc is empty and the call effectively cannot fail
on the unicast path. But on FW reset reopen (bnxt_fw_reset_task ->
bnxt_open) a VF may have a populated dev->uc and the PF may be
transiently unavailable; since that path doesn't go through
__dev_open(), the follow-up rx_mode call that would otherwise drive
the core retry doesn't fire. On -EAGAIN, swallow the error and call
netif_rx_mode_schedule_retry() explicitly. The unicast filter loop
truncates vnic->uc_filter_count on failure, so the retry's delta check
sees pending work and reinstalls.

Cc: Pavan Chebbi <pavan.chebbi@broadcom.com>
Signed-off-by: Stanislav Fomichev <sdf@fomichev.me>
Reviewed-by: Michael Chan <michael.chan@broadcom.com>
Link: https://patch.msgid.link/20260608154014.227538-4-sdf@fomichev.me
Signed-off-by: Jakub Kicinski <kuba@kernel.org>