ARM: sa1111: only setup DMA for DMA capable devices

It's pointless registering the PS/2 interfaces with the dmabounce code
when there's no DMA support for these in hardware, so only setup the
DMA masks for two subdevices which support DMA - the OHCI and SAC.

Acked-by: Nicolas Pitre <nico@linaro.org>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>