dpll: zl3073x: Add support to get/set frequency on pins

Add support to get/set frequency on pins. The frequency for input
pins (references) is computed in the device according this formula:

 freq = base_freq * multiplier * (nominator / denominator)

where the base_freq comes from the list of supported base frequencies
and other parameters are arbitrary numbers. All these parameters are
16-bit unsigned integers.

The frequency for output pin is determined by the frequency of
synthesizer the output pin is connected to and divisor of the output
to which is the given pin belongs. The resulting frequency of the
P-pin and the N-pin from this output pair depends on the signal
format of this output pair.

The device supports so-called N-divided signal formats where for the
N-pin there is an additional divisor. The frequencies for both pins
from such output pair are computed:

 P-pin-freq = synth_freq / output_div
 N-pin-freq = synth_freq / output_div / n_div

For other signal-format types both P and N pin have the same frequency
based only synth frequency and output divisor.

Implement output pin callbacks to get and set frequency. The frequency
setting for the output non-N-divided signal format is simple as we have
to compute just new output divisor. For N-divided formats it is more
complex because by changing of output divisor we change frequency for
both P and N pins. In this case if we are changing frequency for P-pin
we have to compute also new N-divisor for N-pin to keep its current
frequency. From this and the above it follows that the frequency of
the N-pin cannot be higher than the frequency of the P-pin and the
callback must take this limitation into account.

Co-developed-by: Prathosh Satish <Prathosh.Satish@microchip.com>
Signed-off-by: Prathosh Satish <Prathosh.Satish@microchip.com>
Signed-off-by: Ivan Vecera <ivecera@redhat.com>
Reviewed-by: Jiri Pirko <jiri@nvidia.com>
Link: https://patch.msgid.link/20250704182202.1641943-13-ivecera@redhat.com


Signed-off-by: Jakub Kicinski <kuba@kernel.org>