drm/xe: Update xe2_graphics name string

drm/xe: Update xe2_graphics name string

Since both Xe2 and Xe3 platforms currently use the same set of graphics
IP feature flags, we associate the "graphics_xe2" structure with both IPs.
Update the name string on that IP structure to clarify this and avoid
confusion as Xe3 platforms start going into public CI.

Fixes: 800d75bf20ae ("drm/xe/xe3: Define Xe3 feature flags")
Signed-off-by: Matt Roper <matthew.d.roper@intel.com>
Reviewed-by: Vinay Belgaumkar <vinay.belgaumkar@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20241125194838.1190599-2-matthew.d.roper@intel.com