drm/i915/dpll: Rename intel_shared_dpll

Rename intel_shared_dpll to intel_dpll to represent both
shared and individual dplls. Since from MTL each PHY has it's
own PLL making the shared PLL naming a little outdated. In an
effort to make this framework accepting of future changes this
needs to be done.

--v2
-Use intel_dpll_global to make sure names start with the filename
[Jani/Ville]
-Explain the need of this rename [Jani]

--v3
-Just keep it intel_dpll [Jani]

--v4
-Fix comment [Jani]
-Use just num_dpll and dplls [Jani]

Signed-off-by: Suraj Kandpal <suraj.kandpal@intel.com>
Reviewed-by: Jani Nikula <jani.nikula@intel.com>
Link: https://lore.kernel.org/r/20250515071801.2221120-7-suraj.kandpal@intel.com