drm/i915/dram: move fsb_freq and mem_freq to dram info

drm/i915/dram: move fsb_freq and mem_freq to dram info

Store fsb_freq and mem_freq in dram info the same way we do for other
memory info on later platforms for a slightly more unified approach.

This allows us to remove fsb_freq, mem_freq and is_ddr3 members from
struct drm_i915_private and struct xe_device.

Reviewed-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
Link: https://lore.kernel.org/r/a38c4b105ba9098fa0b128cb86cd4eb63bcc27e8.1755511595.git.jani.nikula@intel.com
Signed-off-by: Jani Nikula <jani.nikula@intel.com>