dpll: expose fractional frequency offset value to user

Add a new netlink attribute to expose fractional frequency offset value
for a pin. Add an op to get the value from the driver.

Signed-off-by: Jiri Pirko <jiri@nvidia.com>
Acked-by: Vadim Fedorenko <vadim.fedorenko@linux.dev>
Acked-by: Arkadiusz Kubalewski <arkadiusz.kubalewski@intel.com>
Link: https://lore.kernel.org/r/20240103132838.1501801-2-jiri@resnulli.us


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