drm/i915/dpll: Rename intel_reference_dpll_crtc

Rename intel_reference_dpll_crtc to intel_dpll_crtc_get in an
effort to have all the exported functions have the name start
with file name.

Signed-off-by: Suraj Kandpal <suraj.kandpal@intel.com>
Reviewed-by: Mika Kahola <mika.kahola@intel.com>
Link: https://lore.kernel.org/r/20250515071801.2221120-12-suraj.kandpal@intel.com