iio: frequency: ad9528: Move register value definitions to dt-bindings

Signed-off-by: Paul Cercueil <paul.cercueil@analog.com>
ARM: dts: FMCADC3: Use macros from dt-bindings for easier reading

Signed-off-by: Paul Cercueil <paul.cercueil@analog.com>
iio: frequency: ad9528: Allow single-ended receiver mode for REFA/B

This is done by separating the adi,ref[a|b]-enable from the
adi,ref[a|b]-diff-rcv-enable options, so that REFA/B can be used in
single-ended receiver mode.

Signed-off-by: Paul Cercueil <paul.cercueil@analog.com>
spi: cadence: Init HW after reading devicetree attributes

Signed-off-by: Paul Cercueil <paul.cercueil@analog.com>