staging: greybus: audio: replace safe list iteration

No entry is being removed from the list when iterating the widget list
in gbaudio_dapm_free_controls() so there's no need to use
list_for_each_entry_safe().

Signed-off-by: Johan Hovold <johan@kernel.org>
Link: https://lore.kernel.org/r/20220610075347.18917-1-johan@kernel.org


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>