iio: frequency: ad9523 round closest

Signed-off-by: Michael Hennerich <michael.hennerich@analog.com>
iio: frequency: ad9122 revise clk rate handling

Signed-off-by: Michael Hennerich <michael.hennerich@analog.com>
iio: adc: cf_axi_adc: misc changes

Reject buffer sizes > 524288 bytes
Introduce ADC max rate
Allow reading in junks < buffer size

Signed-off-by: Michael Hennerich <michael.hennerich@analog.com>