Merge branch 'Introduce-XDP-to-ena'

Sameeh Jubran says:

====================
Introduce XDP to ena

This patchset includes 3 patches:
* XDP_DROP implementation
* XDP_TX implementation
* A fix for an issue which might occur due to the XDP_TX patch. I see fit
  to place it as a standalone patch for clarity.

Difference from v2:
* Fixed the usage of rx headroom (XDP_PACKET_HEADROOM)
* Aligned the page_offset of the packet when passing it to the stack
* Switched to using xdp_frame in xdp xmit queue
* Dropped the print for unsupported commands
* Cosmetic changes

Difference from RFC v1 (XDP_DROP patch):
* Initialized xdp.rxq pointer
* Updated max_mtu on attachment of xdp and removed the check from
  ena_change_mtu()
* Moved the xdp execution from ena_rx_skb() to ena_clean_rx_irq()
* Moved xdp buff (struct xdp_buff) from rx_ring to the local stack
* Started using netlink's extack mechanism to deliver error messages to
  the user
====================

Signed-off-by: David S. Miller <davem@davemloft.net>