drm/i915: Perform manual conversions for crtc uapi/hw split, v2.

intel_get_load_detect_pipe() needs to set uapi active,
uapi enable is set by the call to drm_atomic_set_mode_for_crtc(),
so we can remove it.

intel_pipe_config_compare() needs to look at hw state, but I didn't
change spatch to look at it. It's easy enough to do manually.

intel_atomic_check() definitely needs to check for uapi enable,
otherwise intel_modeset_pipe_config cannot copy uapi state to hw.

Changes since v1:
- Actually set uapi.active in get_load_detect_pipe().

Signed-off-by: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20191031112610.27608-3-maarten.lankhorst@linux.intel.com