dma: intel_adsp: Reduce irq setup code

Makes the IRQ_CONNECT macro statically declarable for Xtensa (nothing
prevented it except its structuring). Allows for IRQ_CONNECT usage
on a xtensa only platform to be declared statically avoiding the
fluff of setting up and enabling irqs for cavs gpdma.

Signed-off-by: Tom Burdick <thomas.burdick@intel.com>