Add support for bcm2837-rpi-cm3-io3.dtb aka. bcm2710-rpi-cm3.dtb

Designed to work for:
 - Raspberry Pi Compute Module 3 (CM3);
 - Raspberry Pi Compute Module 3 Lite (CM3L);
 - Raspberry Pi Compute Module IO Board V3.

DTB generated by the Linux kernel build system: bcm2837-rpi-cm3-io3.dtb
DTB expected by the bootloader: bcm2710-rpi-cm3.dtb

The DTB addition in the linux source package is tracked in #932157.

Tested-by: Charles Fendt <charles.fendt@me.com>
Signed-off-by: Cyril Brulebois <cyril@debamax.com>