drm/i915/display: Add CDCLK Support for MTL

As per bSpec MTL has 38.4 MHz Reference clock.
Adding the cdclk tables and cdclk_funcs that MTL
will use.

v2: Revert to using bxt_get_cdclk()

BSpec: 65243

Cc: Clint Taylor <Clinton.A.Taylor@intel.com>
Signed-off-by: Anusha Srivatsa <anusha.srivatsa@intel.com>
Reviewed-by: Clint Taylor <Clinton.A.Taylor@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20221117230002.792096-3-anusha.srivatsa@intel.com