drm/i915/dpll: Rename intel_update_active_dpll

Rename intel_update_active_dpll to intel_dpll_update_active in an
effort to have function names which are exported to start with
filenames they are exported from.

Signed-off-by: Suraj Kandpal <suraj.kandpal@intel.com>
Reviewed-by: Mika Kahola <mika.kahola@intel.com>
Link: https://lore.kernel.org/r/20250515071801.2221120-15-suraj.kandpal@intel.com