drm/i915: prefer 3-letter acronym for icelake

drm/i915: prefer 3-letter acronym for icelake

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 icelake to icl where appropriate.

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/20191224084012.24241-6-lucas.demarchi@intel.com