rtc: rtc-m48t86: add devicetree bindings

This patch allows rtc-m48t86 to be used via devicetree.

Signed-off-by: Alexander Clouter <alex@digriz.org.uk>
arm: orion5x: fixup ts78xx to be able to used the rtc-m48t86 again.

Signed-off-by: Alexander Clouter <alex@digriz.org.uk>
arm: ep93xx: fixup ts72xx to be able to used the rtc-m48t86 again.

Signed-off-by: Alexander Clouter <alex@digriz.org.uk>
arm: orion5x: hook in the RTC into the DT for the TS-7800

Make the DT version of TS-7800 use its RTC.

Signed-off-by: Alexander Clouter <alex@digriz.org.uk>