igb: Introduce igb_xdp_is_enabled()

igb: Introduce igb_xdp_is_enabled()

Introduce igb_xdp_is_enabled() to check if an XDP program is assigned to
the device. Use that wherever xdp_prog is read and evaluated.

Signed-off-by: Sriram Yagnaraman <sriram.yagnaraman@est.tech>
[Kurt: Split patches and use READ_ONCE()]
Signed-off-by: Kurt Kanzenbach <kurt@linutronix.de>
Acked-by: Maciej Fijalkowski <maciej.fijalkowski@intel.com>
Tested-by: George Kuruvinakunnel <george.kuruvinakunnel@intel.com>
Signed-off-by: Tony Nguyen <anthony.l.nguyen@intel.com>
Link: https://patch.msgid.link/20250106221929.956999-3-anthony.l.nguyen@intel.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>