drm/i915: Rename PLL hw_state variables/arguments

drm/i915: Rename PLL hw_state variables/arguments

We have zero consistency in out PLL state naming scheme. Try
to unify things a bit by using 'dpll_hw_state' for high level
stuff and just 'hw_state' for low level stuff. Currently both
are the same, but I want to unionize intel_dpll_hw_state at
which point using different names can make it more clear whether
we're talking about the whole union or just the embedded platform
specific struct.

Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20240412182703.19916-4-ville.syrjala@linux.intel.com
Reviewed-by: Jani Nikula <jani.nikula@intel.com>