bnxt_en: Refactor VNIC alloc and cfg functions

The current VNIC structures are stored in an array bp->vnic_info[].
The index of the array (vnic_id) is passed to all the functions that
need to reference the VNIC.

This patch changes the scheme to pass the VNIC pointer instead of the
vnic index.  Subsequent patches will create additional VNICs that
will not be stored in the bp->vnic_info[] array.  Using the VNIC
pointer will work for all the VNICs.

Reviewed-by: Kalesh AP <kalesh-anakkur.purayil@broadcom.com>
Signed-off-by: Pavan Chebbi <pavan.chebbi@broadcom.com>
Signed-off-by: Michael Chan <michael.chan@broadcom.com>
Link: https://lore.kernel.org/r/20240325222902.220712-5-michael.chan@broadcom.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>