doc: dt: add documentation for alphascale,asm9260-rtc

Document Alphascale asm9260 RTC bindings

Signed-off-by: Oleksij Rempel <linux@rempel-privat.de>
Acked-by: Rob Herring <robh@kernel.org>
Signed-off-by: Alexandre Belloni <alexandre.belloni@free-electrons.com>
1 file changed