Fix the following W=1 kernel warnings:

drivers/gpu/drm/i915/gvt/mmio_context.c:560: warning: expecting
prototype for intel_gvt_switch_render_mmio(). Prototype was for
intel_gvt_switch_mmio() instead.
Reported-by: Abaci Robot <abaci@linux.alibaba.com>
Signed-off-by: Jiapeng Chong <jiapeng.chong@linux.alibaba.com>
Signed-off-by: Zhenyu Wang <zhenyuw@linux.intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/20220524083733.67148-1-jiapeng.chong@linux.alibaba.comAcked-by: Zhenyu Wang <zhenyuw@linux.intel.com>