drm/i915/gvt: filter cmds "srm" and "lrm" in cmd_handler

do not allow "srm" and "lrm" except for GEN8_L3SQCREG4 and 0x21f0.

Cc: Colin Xu <colin.xu@intel.com>
Cc: Kevin Tian <kevin.tian@intel.com>
Signed-off-by: Yan Zhao <yan.y.zhao@intel.com>
Signed-off-by: Zhenyu Wang <zhenyuw@linux.intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/20201223034508.17031-1-yan.y.zhao@intel.com


Reviewed-by: Zhenyu Wang <zhenyuw@linux.intel.com>