drm/i915: Simplify cdclk_disable_noatomic()

Instead of hand rolling the cdclk state disabling for a
pipe in noatomic() let's just recompute the whole thing
from scratch. Less code we have to remember to keep in sync.

Reviewed-by: Vinod Govindapillai <vinod.govindapillai@intel.com>
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20250306163420.3961-15-ville.syrjala@linux.intel.com