[ARM] 4908/1: [AT91] RTT platform_device fix

The RTT-as-RTC driver will search for the user-specified RTT
peripheral via ID number (0 .. 1).
Therefore if the processor only contains a single RTT peripheral, we
need to set its platform_device.id to "0" instead of "-1".
Also add the missing platform_device resource for the CAP9 processor.

Bug reported by Sedji Gaouaou.

Signed-off-by: Andrew Victor <linux@maxim.org.za>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>