drm/i915: move a Kconfig symbol to unbreak the menu presentation

Inserting a Kconfig symbol that does not have a dependency (DRM_I915_GVT)
into a list of other symbols that do have a dependency (on DRM_I915)
breaks the driver menu presentation in 'make *config'.

Relocate the DRM_I915_GVT symbol so that it does not cause this
problem.

Fixes: 8b750bf7

 ("drm/i915/gvt: move the gvt code into kvmgt.ko")
Signed-off-by: Randy Dunlap <rdunlap@infradead.org>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Zhi Wang <zhi.a.wang@intel.com>
Cc: Jani Nikula <jani.nikula@linux.intel.com>
Cc: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Cc: Rodrigo Vivi <rodrigo.vivi@intel.com>
Cc: Tvrtko Ursulin <tvrtko.ursulin@linux.intel.com>
Cc: Zhenyu Wang <zhenyuw@linux.intel.com>
Cc: intel-gfx@lists.freedesktop.org
Cc: intel-gvt-dev@lists.freedesktop.org
Cc: dri-devel@lists.freedesktop.org
Reviewed-by: Christoph Hellwig <hch@lst.de>
Acked-by: Zhenyu Wang <zhenyuw@linux.intel.com>
Signed-off-by: Zhenyu Wang <zhenyuw@linux.intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/20230215044533.4847-1-rdunlap@infradead.org