drm/i915/gvt: Fix gen8/9_render_mmio_list[0] don't take effect

drm/i915/gvt: Fix gen8/9_render_mmio_list[0] don't take effect

while(mmio++) increase mmio to next, mmio[0] never take effect
in while loop.

This patch change while to for and fix the above issue.

v2: Correct Fixes format.(Zhenyu)
v3: Rebase to latest staging.(Zhenyu)

Fixes: f609c73cf6d2("drm/i915/gvt: Select appropriate mmio list at initialization time")
Signed-off-by: Xiong Zhang <xiong.y.zhang@intel.com>
Signed-off-by: Zhenyu Wang <zhenyuw@linux.intel.com>
Signed-off-by: Rodrigo Vivi <rodrigo.vivi@intel.com>