bnxt: Add XDP frame size to driver

This driver uses full PAGE_SIZE pages when XDP is enabled.

In case of XDP uses driver uses __bnxt_alloc_rx_page which does full
page DMA-map. Thus, xdp_adjust_tail grow is DMA compliant for XDP_TX
action that does DMA-sync.

Signed-off-by: Jesper Dangaard Brouer <brouer@redhat.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Reviewed-by: Andy Gospodarek <gospo@broadcom.com>
Cc: Michael Chan <michael.chan@broadcom.com>
Cc: Andy Gospodarek <andrew.gospodarek@broadcom.com>
Link: https://lore.kernel.org/bpf/158945334769.97035.13437970179897613984.stgit@firesoul