[media] v4l: vsp1: Fix VI6_DPR_ROUTE_FXA_MASK macro

FXA bit of VI6_DPR_mod_ROUTE register starts from 16bit. But VI6_DPR_ROUTE_FXA_MASK
is set to become start from 8bit. This fixes shift size for VI6_DPR_ROUTE_FXA_MASK.

Signed-off-by: Nobuhiro Iwamatsu <nobuhiro.iwamatsu.yj@renesas.com>
Signed-off-by: Laurent Pinchart <laurent.pinchart+renesas@ideasonboard.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@osg.samsung.com>