drm/i915/dram: bypass fsb/mem freq detection on dg2 and no display

drm/i915/dram: bypass fsb/mem freq detection on dg2 and no display

Non-display now calls the intel_fsb_freq() and intel_mem_freq()
functions, so we don't have to have the frequencies initialized for dg2
or non-display cases.

This is in preparation for unifying the pre-gen9 handling in dram info.

DG2 remains a special case as described in commit 5eb6bf0b44e7
("drm/i915/dg2: Don't read DRAM info").

v2: Rebase

Reviewed-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
Link: https://lore.kernel.org/r/7bfed06d431354f3918ea73d43a2ec8ed9426a76.1755511595.git.jani.nikula@intel.com
Signed-off-by: Jani Nikula <jani.nikula@intel.com>