clk: at91: enable AUDIOPLL as source for PCKx on SAMA5D2

Datasheet for SAMA5D2x mentions 6 sources for PCKx, the last being AUDIOPLL.

Signed-off-by: Michał Mirosław <mirq-linux@rere.qmqm.pl>
Acked-by: Alexandre Belloni <alexandre.belloni@bootlin.com>
Signed-off-by: Stephen Boyd <sboyd@kernel.org>