dpll: zl3073x: Remove unused dev wrappers

dpll: zl3073x: Remove unused dev wrappers

Remove several zl3073x_dev_... inline wrapper functions from core.h
as they are no longer used by any callers.

Removed functions:
* zl3073x_dev_ref_ffo_get
* zl3073x_dev_ref_is_enabled
* zl3073x_dev_synth_dpll_get
* zl3073x_dev_synth_is_enabled
* zl3073x_dev_out_signal_format_get

This is a cleanup after recent refactoring, as the remaining callers
now fetch the state object and use the base helpers directly.

Reviewed-by: Petr Oros <poros@redhat.com>
Tested-by: Prathosh Satish <Prathosh.Satish@microchip.com>
Signed-off-by: Ivan Vecera <ivecera@redhat.com>
Link: https://patch.msgid.link/20251113074105.141379-7-ivecera@redhat.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>