drm/i915: add macros for graphics and media versions

Like it was done in
commit 01eb15c9 ("drm/i915: Add DISPLAY_VER() and related macros")
add the correspondent macros for graphics and media. Going forward we
will prefer checking the versions for the specific IPs (graphics, media
and display) rather than grouping everything under a "gen" version.

For consistency and to make the maintenance easier, it'd be preferred
not to mix the *GEN* macros with the new ones. For older platforms we
can simply consider that the previous "gen" number will extend to all
3 IPs. Then we can start replacing its use in the driver. Right now this
replacement is not done and only the infrastructure is put in place.
We also leave gen and gen_mask inside struct intel_device_info while
it's still being used throughout the code.

v2: Repurpose IS_{GRAPHICS,MEDIA}_VER() macros to work with a range

Signed-off-by: Lucas De Marchi <lucas.demarchi@intel.com>
Reviewed-by: José Roberto de Souza <jose.souza@intel.com>
Reviewed-by: Jani Nikula <jani.nikula@intel.com>
[Jani: Minor code comment change while applying.]
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20210413051002.92589-5-lucas.demarchi@intel.com