xsk: Move NETDEV_XDP_ACT_ZC into generic header

xsk: Move NETDEV_XDP_ACT_ZC into generic header

Move NETDEV_XDP_ACT_ZC into xdp_sock_drv.h header such that external code
can reuse it, and rename it into more generic NETDEV_XDP_ACT_XSK.

Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Co-developed-by: David Wei <dw@davidwei.uk>
Signed-off-by: David Wei <dw@davidwei.uk>
Reviewed-by: Maciej Fijalkowski <maciej.fijalkowski@intel.com>
Reviewed-by: Nikolay Aleksandrov <razor@blackwall.org>
Link: https://patch.msgid.link/20251031212103.310683-7-daniel@iogearbox.net
Signed-off-by: Jakub Kicinski <kuba@kernel.org>