drm/i915/gvt: correct a false comment of flag F_UNALIGN

drm/i915/gvt: correct a false comment of flag F_UNALIGN

Correct falsely removed comment of flag F_UNALIGN.

Fixes: a6c5817a38cf ("drm/i915/gvt: remove flag F_CMD_ACCESSED")
Reviewed-by: Zhenyu Wang <zhenyuw@linux.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/20200910035405.20273-1-yan.y.zhao@intel.com
(cherry picked from commit 6594094f819e0020e926e137e47e2edb97ba500b)
Signed-off-by: Rodrigo Vivi <rodrigo.vivi@intel.com>