drm/i915: rename display.version to display.ver

The macro we use to check is called DISPLAY_VER(). While using this
macro and the new ones being added in following changes I made the
mistake multiple times when mixing both "ver" and "version". Although
it's usually better to prefer the complete name, the shorhand
DISPLAY_VER() / GRAPHICS_VER / MEDIA_VER are clear and cause less
visual polution.

Another issue is when copying the variable to other places.
"display.version" would be copied to a "display_version" variable which
is long and would make people abbreviate as "version", or "display_ver".
In the first case it's not always clear what version refers to, and in
the second case it just hints it should be the name in the first place.

So, in the same way use used "gen" rather than "generation", use "ver"
instead of "version".

Signed-off-by: Lucas De Marchi <lucas.demarchi@intel.com>
Reviewed-by: José Roberto de Souza <jose.souza@intel.com>
Acked-by: Jani Nikula <jani.nikula@intel.com>
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20210413051002.92589-3-lucas.demarchi@intel.com