drm/msm/mdp4: add LVDS panel support

LVDS panel support uses the LCDC (parallel) encoder.  Unlike with HDMI,
there is not a separate LVDS block, so no need to split things into a
bridge+connector.  Nor is there is anything re-used with mdp5.

Note that there can be some regulators shared between HDMI and LVDS (in
particular, on apq8064, ext_3v3p), so we should not use the _exclusive()
variants of devm_regulator_get().

The drm_panel framework is used for panel-specific driver.

Signed-off-by: Rob Clark <robdclark@gmail.com>

drivers/gpu/drm/msm/Kconfig

@@ -4,6 +4,7 @@ config DRM_MSM
 	depends on DRM
 	depends on ARCH_QCOM || (ARM && COMPILE_TEST)
 	select DRM_KMS_HELPER
+	select DRM_PANEL
 	select SHMEM
 	select TMPFS
 	default y