drm/i915: Prevent HW access during init from SDVO TV get_modes hook

drm/i915: Prevent HW access during init from SDVO TV get_modes hook

Prevent accessing the HW from the SDVO/TV get_modes connector hook.
Returning 0 from the hook will make the caller -
drm_helper_probe_single_connector_modes() - return a default/EDID
override mode list to users. This matches the case where
intel_sdvo_get_tv_modes() fails to retrieve the current mode list due to
a HW access failure.

v2: Clarify the commit message wrt. which modes get_modes() returns. (Jouni)

Signed-off-by: Imre Deak <imre.deak@intel.com>
Reviewed-by: Jouni Högander <jouni.hogander@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20240212175237.2625812-1-imre.deak@intel.com