drm/i915/display: identify discrete graphics

drm/i915/display: identify discrete graphics

Identify discrete graphics separately in display, using the platform
group mechanism. This enables dropping the dependency on i915_drv.h
IS_DGFX() from display code.

Start grouping platform groups separately in INTEL_DISPLAY_PLATFORMS()
in anticipation of more groups to come.

Reviewed-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/c02230d26cc0d9dbd7ddcc064661b2ad03739b6a.1731321183.git.jani.nikula@intel.com
Signed-off-by: Jani Nikula <jani.nikula@intel.com>