vc04_services: bcm2835_codec: Allow larger images through the ISP

Whilst the codecs are restricted to 1920x1080 / 1080x1920, the ISP
isn't, but the limits advertised via V4L2 was 1920x1920 for all
roles.

Increase the limit to 16k x 16k for the ISP.

Signed-off-by: Dave Stevenson <dave.stevenson@raspberrypi.com>