[ARM] DSM320: Update KS8695 defconfig to include DSM320

Update the KS8695 defconfig to bring it up to modern config
standards and include the DSM320 and appropriate drivers for the
DSM320 (E.g. prism54).

Signed-off-by: Daniel Silverstone <dsilvers@simtec.co.uk>
Signed-off-by: Ben Dooks <ben-linux@fluff.org>