kms_addfb_basic: Get intel gen from within subtest

Because determining the Intel GFX generation requires a call to
DRM_IOCTL_I915_GETPARAM, move the code that requires it to a subtest
that can be skipped on drivers other than i915.

Signed-off-by: Tomeu Vizoso <tomeu.vizoso@collabora.com>
Reviewed-by: Daniel Stone <daniels@collabora.com>
Acked-by: Daniel Vetter <daniel.vetter@ffwll.ch>
1 file changed