[ARM] 4748/1: dca: source drivers/dca/Kconfig in arch/arm/Kconfig to fix warning

'select' used by config symbol 'INTEL_IOATDMA' refers to undefined symbol 'DCA'

Although drivers/dma is currently the only user future drivers outside of
drivers/dma may select this option so it is better to add this to
arch/arm/Kconfig than move DCA to drivers/dma/Kconfig.

Signed-off-by: Dan Williams <dan.j.williams@intel.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>