drm/i915/gvt: Annotate iomem usage

Fix the sparse warning for blithely using iomem with normal memcpy:

drivers/gpu/drm/i915/gvt/kvmgt.c:916:21: warning: incorrect type in assignment (different address spaces)
drivers/gpu/drm/i915/gvt/kvmgt.c:916:21:    expected void *aperture_va
drivers/gpu/drm/i915/gvt/kvmgt.c:916:21:    got void [noderef] <asn:2> *
drivers/gpu/drm/i915/gvt/kvmgt.c:927:26: warning: incorrect type in argument 1 (different address spaces)
drivers/gpu/drm/i915/gvt/kvmgt.c:927:26:    expected void [noderef] <asn:2> *vaddr
drivers/gpu/drm/i915/gvt/kvmgt.c:927:26:    got void *aperture_va

Fixes: d480b28a ("drm/i915/gvt: Fix aperture read/write emulation when enable x-no-mmap=on")
Reviewed-by: Zhenyu Wang <zhenyuw@linux.intel.com>
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Zhenyu Wang <zhenyuw@linux.intel.com>
Cc: Changbin Du <changbin.du@intel.com>
Cc: Zhi Wang <zhi.a.wang@intel.com>
Signed-off-by: Zhenyu Wang <zhenyuw@linux.intel.com>