net: ena: introduce XDP redirect implementation

This patch adds a partial support for the XDP_REDIRECT directive which
instructs the driver to pass the packet to an interface specified by the
program. The directive is passed to the driver by calling bpf_redirect()
or bpf_redirect_map() functions from the eBPF program.

To lay the ground for integration with the existing XDP TX
implementation the patch removes the redundant page ref count increase
in ena_xdp_xmit_frame() and then decrease in ena_clean_rx_irq(). Instead
it only DMA unmaps descriptors for which XDP TX or REDIRECT directive
was received.

The XDP Redirect support is still missing .ndo_xdp_xmit function
implementation, which allows to redirect packet to an ENA interface,
which would be added in a later patch.

Signed-off-by: Shay Agroskin <shayagr@amazon.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>