drm/i915/dpll: Rename intel_compute_dpll

Rename intel_compute_dpll to intel_dpll_compute in an
effort to make sure all function names that are exported have
the filename at start.

Signed-off-by: Suraj Kandpal <suraj.kandpal@intel.com>
Reviewed-by: Jani Nikula <jani.nikula@intel.com>
Link: https://lore.kernel.org/r/20250515071801.2221120-14-suraj.kandpal@intel.com