drm/i915/display: Avoid unnecessarily calling intel_cx0_get_owned_lane_mask

Currently we are always calling intel_cx0_get_owned_lane_mask when
intel_lnl_mac_transmit_lfps is called. Avoid this in cases where it's not
needed.

Signed-off-by: Jouni Högander <jouni.hogander@intel.com>
Reviewed-by: Gustavo Sousa <gustavo.sousa@intel.com>
Link: https://lore.kernel.org/r/20250722125618.1842615-3-jouni.hogander@intel.com