drm/i915/icl: Refactor icl pll functions

drm/i915/icl: Refactor icl pll functions

This patch adds helper function for identifying
whether the given PLL is combo PHY PLL or not.
This helper function is used inside various ICL
functions to make them scalable.

Signed-off-by: Vandita Kulkarni <[email protected]>
Signed-off-by: Mahesh Kumar <[email protected]>
Cc: Madhav Chauhan <[email protected]>
Cc: Lucas De Marchi <[email protected]>
Reviewed-by: Lucas De Marchi <[email protected]>
Signed-off-by: Rodrigo Vivi <[email protected]>
Link: https://patchwork.freedesktop.org/patch/msgid/[email protected]