drm: vc4: 0 is a valid value for pixel_order_hvs5, so fix conditionals

vc4_plane_mode_set for HVS5 was using pixel_order unless pixel_order_hvs5
was non-zero, except 0 is a valid value for the pixel_order.

Specify pixel_order_hvs5 for all formats and remove the conditional.

Reported-by: vrazzer <teamvraz@pipmail.net>
Signed-off-by: Dave Stevenson <dave.stevenson@raspberrypi.com>