drm/i915/pch: Make LPT LP a dedicated PCH type

drm/i915/pch: Make LPT LP a dedicated PCH type

Add PCH type PCH_LPT_LP and rename PCH_LPT to PCH_LPT_H for
consistency. Keep the existing HAS_PCH_LPT*() macros, but express them
in terms of the PCH types instead of looking at the device IDs
directly. This makes the PCH checks independent of the PCH device IDs.

Reviewed-by: Nemesa Garg <nemesa.garg@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/777b63f50b10fba1d768af25870e81b33267bdc8.1738923308.git.jani.nikula@intel.com
Signed-off-by: Jani Nikula <jani.nikula@intel.com>