drm/i915: prefer 3-letter acronym for pineview

We are currently using a mix of platform name and acronym to name the
functions. Let's prefer the acronym as it should be clear what platform
it's about and it's shorter, so it doesn't go over 80 columns in a few
cases. This converts pineview to pnv where appropriate.

v2: Add missing conversions in intel_pm.c (Matt Roper). While at it, fix
missing blank lines between structs that would otherwise trigger
checkpatch errors (Lucas)

Signed-off-by: Lucas De Marchi <lucas.demarchi@intel.com>
Acked-by: Jani Nikula <jani.nikula@linux.intel.com>
Acked-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Reviewed-by: Matt Roper <matthew.d.roper@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20191224084012.24241-2-lucas.demarchi@intel.com