mfd : Cleanup duplicate db8500 definitions

I missed in my previous patch the A9_MASK_REQ[_MASK] were
already defined. Let's remove the duplicate definitions.

The PRCMU_GIC_DELAY macro could be removed as it is not
really useful here.

Signed-off-by: Daniel Lezcano <daniel.lezcano@linaro.org>
Signed-off-by: Samuel Ortiz <sameo@linux.intel.com>