drm/i915/ddi: add wrapper for calling ->get_buf_trans() hook

drm/i915/ddi: add wrapper for calling ->get_buf_trans() hook

Add intel_ddi_buf_trans_get() wrapper for calling the
encoder->get_buf_trans() hooks, allowing for a centralized place to
e.g. check for VBT overrides for the buf translations.

Cc: Michał Grzelak <michal.grzelak@intel.com>
Reviewed-by: Suraj Kandpal <suraj.kandpal@intel.com>
Link: https://patch.msgid.link/20260415115104.1721008-1-jani.nikula@intel.com
Signed-off-by: Jani Nikula <jani.nikula@intel.com>