dpll: zl3073x: Implement input pin selection in manual mode

dpll: zl3073x: Implement input pin selection in manual mode

Implement input pin state setting if the DPLL is running in manual mode.
The driver indicates manual mode if the DPLL mode is one of ref-lock,
forced-holdover, freerun.

Use these modes to implement input pin state change between connected
and disconnected states. When the user set the particular pin as
connected the driver marks this input pin as forced reference and
switches the DPLL mode to ref-lock. When the use set the pin as
disconnected the driver switches the DPLL to freerun or forced holdover
mode. The switch to holdover mode is done if the DPLL has holdover
capability (e.g is currently locked with holdover acquired).

Signed-off-by: Ivan Vecera <ivecera@redhat.com>
Reviewed-by: Jiri Pirko <jiri@nvidia.com>
Link: https://patch.msgid.link/20250704182202.1641943-10-ivecera@redhat.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>