drm/panel: fix unmet dependency bug for DRM_PANEL_HIMAX_HX83121A

drm/panel: fix unmet dependency bug for DRM_PANEL_HIMAX_HX83121A

Currently, DRM_PANEL_HIMAX_HX83121A selects DRM_DISPLAY_DSC_HELPER
without also ensuring DRM_DISPLAY_HELPER is enabled, causing an unmet
dependency:

WARNING: unmet direct dependencies detected for DRM_DISPLAY_DSC_HELPER
  Depends on [n]: HAS_IOMEM [=y] && DRM [=m] && DRM_DISPLAY_HELPER [=n]
  Selected by [m]:
  - DRM_PANEL_HIMAX_HX83121A [=m] && HAS_IOMEM [=y] && DRM [=m] && DRM_PANEL [=y] && OF [=y] && DRM_MIPI_DSI [=y] && BACKLIGHT_CLASS_DEVICE [=m]
  - DRM_PANEL_ILITEK_ILI9882T [=m] && HAS_IOMEM [=y] && DRM [=m] && DRM_PANEL [=y] && OF [=y] && DRM_MIPI_DSI [=y] && BACKLIGHT_CLASS_DEVICE [=m]

Many other DRM_PANEL_* options select DRM_DISPLAY_HELPER when selecting
DRM_DISPLAY_DSC_HELPER, let's do the same here.

This unmet dependency bug was found by kconfirm, a static analysis tool
for Kconfig.

Fixes: defab7b01e08 ("drm/panel: hx83121a: select DRM_DISPLAY_DSC_HELPER")
Signed-off-by: Julian Braha <julianbraha@gmail.com>
Reviewed-by: Neil Armstrong <neil.armstrong@linaro.org>
Signed-off-by: Neil Armstrong <neil.armstrong@linaro.org>
Link: https://patch.msgid.link/20260711234230.2236041-1-julianbraha@gmail.com