drm/omap/hdmi5: switch to ->edid_read callback

Prefer using the struct drm_edid based callback and functions.

Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Reviewed-by: Neil Armstrong <neil.armstrong@linaro.org>
Link: https://patchwork.freedesktop.org/patch/msgid/da96653c111a7f989c7c804923968fa5f47c6b5a.1706038510.git.jani.nikula@intel.com