dpll: zl3073x: drop selected and simplify connected ref getter

dpll: zl3073x: drop selected and simplify connected ref getter

The HW reports the currently selected reference in the
dpll_refsel_status register regardless of the DPLL mode. Use this to
delete zl3073x_dpll_selected_ref_get() and have callers read the
register directly via the cached channel state.

Simplify zl3073x_dpll_connected_ref_get() to check refsel_state for
LOCK directly and return the reference index, changing the return
type from int to u8. The redundant ref_is_status_ok check is removed
since the DPLL cannot be in LOCK state with a failed reference.

In zl3073x_dpll_mode_set(), replace the selected_ref_get() call with
zl3073x_chan_refsel_ref_get() to read the currently selected
reference directly from the cached channel state.

Signed-off-by: Ivan Vecera <ivecera@redhat.com>
Link: https://patch.msgid.link/20260315174224.399074-7-ivecera@redhat.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>