drm/i915/gvt: avoid useless use of inline

In most cases, we are better off letting the compiler decide whether to
inline static functions in .c files or not. In this case, the inline
will be ignored anyway as mmio_pm_restore_handler() is passed as a
function pointer.

Fixes: 5f60b12e ("drm/i915/gvt: Save/restore HW status to support GVT suspend/resume")
Cc: Zhenyu Wang <zhenyuw@linux.intel.com>
Cc: Hang Yuan <hang.yuan@linux.intel.com>
Cc: Colin Xu <colin.xu@intel.com>
Cc: Zhi Wang <zhi.a.wang@intel.com>
Cc: intel-gvt-dev@lists.freedesktop.org
Reviewed-by: Zhenyu Wang <zhenyuw@linux.intel.com>
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Signed-off-by: Zhenyu Wang <zhenyuw@linux.intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/20201130111353.25406-1-jani.nikula@intel.com