drm/display: Fix HDMI state helper dependency

During the life of the series that introduced the
DRM_DISPLAY_HDMI_STATE_HELPER option, we reworked the Kconfig option
dependency setup to rely on depends on with commit f6d2dc03fa85 ("drm:
Switch DRM_DISPLAY_HDMI_HELPER to depends on") which got reverted later
on because it was creating too many issues by commit d7c128cb775e
("Revert "drm: Switch DRM_DISPLAY_HDMI_HELPER to depends on"").

However, since the series was out of tree at that time,
DRM_DISPLAY_HDMI_STATE_HELPER wasn't properly updated to take the revert
into account and is now creating build issues.

Let's switch the depends on to a select to fix this.

Reported-by: kernel test robot <lkp@intel.com>
Closes: https://lore.kernel.org/oe-kbuild-all/202405290332.Sqtt0ix0-lkp@intel.com/
Closes: https://lore.kernel.org/oe-kbuild-all/202405290438.TOYhXMIn-lkp@intel.com/
Closes: https://lore.kernel.org/oe-kbuild-all/202405290803.c3178DYT-lkp@intel.com/
Closes: https://lore.kernel.org/oe-kbuild-all/202405291109.PQdqc46g-lkp@intel.com/
Closes: https://lore.kernel.org/oe-kbuild-all/202405291221.a0NStxHE-lkp@intel.com/
Closes: https://lore.kernel.org/oe-kbuild-all/202405291636.8GgBtK8u-lkp@intel.com/
Fixes: 54cb39e2293b ("drm/connector: hdmi: Create an HDMI sub-state")
Reviewed-by: Javier Martinez Canillas <javierm@redhat.com>
Reviewed-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20240529080013.2325748-1-mripard@kernel.org
Signed-off-by: Maxime Ripard <mripard@kernel.org>