drm/i915: Update crtc scaler settings when update_pipe is set

When the pipe_config's update_pipe flag is set we may need to update the
panel fitting settings. On GEN9+ this means we need to update the crtc's
scaler settings.

This fixes the following WARN_ON, during i915 loading on an Asrock
B150M Pro4S/D3 board with an i5-6500 CPU / graphics:

[drm:pipe_config_err [i915]] *ERROR* mismatch in pch_pfit.enabled
 (expected no, found yes)
pipe state doesn't match!
WARNING: CPU: 3 PID: 305 at drivers/gpu/drm/i915/intel_display.c:12084

With line 12084 being the I915_STATE_WARN call inside the
"if (!intel_pipe_config_compare())" block in verify_crtc_state().

On this board with 2 1920x1080 monitors connected over HDMI the GOP
initializes both monitors at 1920x1080 and despite no scaling being
necessary configures a scaler for one of them.

When booting with fastboot=1 on the initial modeset needs_modeset will
be false while update_pipe is true. Since we were not calling
skl_update_scaler_crtc() in this case we would leave the scaler enabled
causing this error.

Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Signed-off-by: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20181217141903.4182-1-hdegoede@redhat.com