[media] v4l: vsp1: Fix typo in VI6_DISP_IRQ_STA_DST register bit name

Rename the VI6_DISP_IRQ_STA_DSE register bit to VI6_DISP_IRQ_STA_DST to
fix a typo and match the datasheet.

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