ice: Refactor ice_setup_rx_ctx

Move AF_XDP logic and buffer allocation out of ice_setup_rx_ctx() to a
new function ice_vsi_cfg_rxq(), so the function actually sets up the Rx
context.

Signed-off-by: Krzysztof Kazimierczak <krzysztof.kazimierczak@intel.com>
Co-developed-by: Tony Nguyen <anthony.l.nguyen@intel.com>
Signed-off-by: Tony Nguyen <anthony.l.nguyen@intel.com>
Tested-by: Kiran Bhandare <kiranx.bhandare@intel.com>