media: vsp1: Fix addresses of display-related registers for VSP-DL

The VSP-DL instances have two LIFs, and thus two copies of the
VI6_DISP_IRQ_ENB, VI6_DISP_IRQ_STA and VI6_WPF_WRBCK_CTRL registers. Fix
the corresponding macros accordingly.

Signed-off-by: Laurent Pinchart <laurent.pinchart+renesas@ideasonboard.com>
Reviewed-by: Kieran Bingham <kieran.bingham+renesas@ideasonboard.com>
Reviewed-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>