staging: vc04_services: isp: Remove duplicated initialisation

With the codec code from which this was derived, the driver had to
get the supported formats for both input and output ports.
This had been copied across, however here we have independent nodes
for each port, but the code had been left in to do the same thing
twice.
Remove the duplicate.

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