drivers/iio/frequency/cf_axi_dds: FMCOMMS5 add support for 8 channel DAC DMA

Signed-off-by: Michael Hennerich <michael.hennerich@analog.com>
Merge branch 'xcomm_zynq_new_pcore_regmap' of https://github.com/analogdevicesinc/linux into xcomm_zynq_new_pcore_regmap