clk: at91: move sam9x60's PLL register offsets to PMC header

Move SAM9X60's PLL register offsets to PMC header so that the
definitions would also be available from arch/arm/mach-at91/pm_suspend.S.
This is necessary to disable/enable PLLA for SAM9X60 on suspend/resume.

Signed-off-by: Claudiu Beznea <claudiu.beznea@microchip.com>
Acked-by: Stephen Boyd <sboyd@kernel.org>
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>
Link: https://lore.kernel.org/r/1579522208-19523-7-git-send-email-claudiu.beznea@microchip.com