drm/i915/tgl: Add the Thunderbolt PLL divider values

The Thunderbolt PLL divider values on TGL differ from the ICL ones,
update the PLL parameter calculation function accordingly.

Bspec: 49204

v2:
- Remove unused refclk config. (José)

Cc: Jose Souza <jose.souza@intel.com>
Cc: Clinton A Taylor <clinton.a.taylor@intel.com>
Cc: Lucas De Marchi <lucas.demarchi@intel.com>
Cc: Mika Westerberg <mika.westerberg@intel.com>
Tested-by: Mika Westerberg <mika.westerberg@intel.com>
Signed-off-by: Imre Deak <imre.deak@intel.com>
Reviewed-by: Jose Souza <jose.souza@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20191002204108.32242-1-imre.deak@intel.com