ad_serdes_in: Update the serdes_in module

Add additional IDELAY block before the ISERDES. Delet the IDDR blocks. Be aware, the ISERDES block are running in DDR mode. If the interface is SDR the maximum parallel data width is 4.
ad9434: Merge the ad9434_if interface data outputs into one single bus
ad9434: Fix the adc to dma interface.

All the device2dma interfaces needs to have a generic form : (data, enable, valid)/channel
ad9434: Fix the processor read interface

Fix the processor read interface, preventing to have nets with multiple drivers. Made a few cosmetic changes in the code too.
ad9434: Fix SPI line physical constraints

SPI lines are not differential.
ad9434: Fix adc_clk constraint

ADC clock is 500 Mhz.