ARM: bcm2835: dts: add thermal node to device-tree of bcm283x

Add the node for the thermal sensor of the bcm2835-soc
to the device tree.

Signed-off-by: Martin Sperl <kernel@martin.sperl.org>
Reviewed-by: Eric Anholt <eric@anholt.net>
Acked-by: Stefan Wahren <stefan.wahren@i2se.com>

Changelog:
V1 -> V5: generic settings is shared in bcm283x.dtsi, but disabled
	  moved the compatible string to the SOC specific dtsi
            for arm and arm64
V5 -> V6: fix remove 0x prefix from thermal@0x7e212000

Note: there is no arm/boot/dts/bcm2837.dtsi as of now,
      so the 32-bit rpi3 dt is not modified.
Signed-off-by: Eric Anholt <eric@anholt.net>