MIPS: SiByte: Enable pata_platform with SWARM defconfig

Enable support for the onboard PATA PIO mode3 interface, which is one of
the boot devices supported by the CFE firmware with the Broadcom SWARM
board.  Include disk, CD-ROM and generic storage drivers.

Signed-off-by: Maciej W. Rozycki <macro@orcam.me.uk>
Signed-off-by: Thomas Bogendoerfer <tsbogend@alpha.franken.de>