ARM: dts: add dts files for bcmbca soc 63178

Add dts for ARMv7 based broadband SoC BCM63178. bcm63178.dtsi is the
SoC description dts header and bcm963178.dts is a simple dts file for
Broadcom BCM963178 Reference board that only enable the UART port.

Signed-off-by: Anand Gore <anand.gore@broadcom.com>
Signed-off-by: Florian Fainelli <f.fainelli@gmail.com>