ARM: digicolor: select syscon and timer

The digicolor interrupt controller driver now needs syscon.

Also, as per clocksource maintainer request, we now have a separate config
symbol, CONFIG_DIGICOLOR_TIMER, for the digicolor timer.

Signed-off-by: Baruch Siach <baruch@tkos.co.il>
Signed-off-by: Olof Johansson <olof@lixom.net>