clk: at91: optimize pmc data allocation

Alloc whole data structure in one block. This makes the code shorter,
more efficient and easier to extend in following patch.

Signed-off-by: Michał Mirosław <mirq-linux@rere.qmqm.pl>
Link: https://lkml.kernel.org/r/fc6f6d67b8cee0beace4a9d9cca7431e5efa769d.1588630999.git.mirq-linux@rere.qmqm.pl


Acked-by: Alexandre Belloni <alexandre.belloni@bootlin.com>
Signed-off-by: Stephen Boyd <sboyd@kernel.org>