drm/i915/gvt: Make DRM_I915_GVT depend on X86

drm/i915/gvt: Make DRM_I915_GVT depend on X86

GVT is not supported on non-x86 platforms, So add
dependency of X86 on config parameter DRM_I915_GVT.

Fixes: 961cbb2863e0 ("drm/i915: gvt: Introduce the basic architecture of GVT-g")
Signed-off-by: Siva Mullati <siva.mullati@intel.com>
Signed-off-by: Zhi Wang <zhi.a.wang@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/20220107095235.243448-1-siva.mullati@intel.com
Reviewed-by: Zhi Wang <zhi.a.wang@intel.com>
Signed-off-by: Zhi Wang <zhi.a.wang@intel.com>