iio: frequency: adf4377: add support for ADF4377

iio: frequency: adf4377: add support for ADF4377

The ADF4377 is a high performance, ultralow jitter, dual output integer-N
phased locked loop (PLL) with integrated voltage controlled oscillator
(VCO) ideally suited for data converter and mixed signal front end (MxFE)
clock applications.

Datasheet: https://www.analog.com/media/en/technical-documentation/data-sheets/adf4377.pdf
Signed-off-by: Antoniu Miclaus <antoniu.miclaus@analog.com>
Reviewed-by: Nuno Sá <nuno.sa@analog.com>
Link: https://lore.kernel.org/r/20221115110041.71495-2-antoniu.miclaus@analog.com
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>