arm: bcmbca: add bcm6878 SoC support

BCM6878 is an ARM A7 based PON Broadband SoC. It is part of the BCA
(Broadband Carrier Access origin) chipset family so it's added under
ARCH_BCMBCA platform. This initial support includes a bare-bone
implementation and dts with CPU subsystem, memory and ARM PL011
uart.

This SoC is supported in the linux-next git repository so the dts and
dtsi files are copied from linux with minor fix-up that needs to be
upstreamed to linux as well.

The u-boot image can be loaded from flash or network to the entry point
address in the memory and boot from there.

Signed-off-by: William Zhang <william.zhang@broadcom.com>
diff --git a/arch/arm/dts/Makefile b/arch/arm/dts/Makefile
index 4ddff6e..d0996a1 100644
--- a/arch/arm/dts/Makefile
+++ b/arch/arm/dts/Makefile
@@ -1186,6 +1186,8 @@
 	bcm963178.dtb
 dtb-$(CONFIG_BCM6846) += \
 	bcm96846.dtb
+dtb-$(CONFIG_BCM6878) += \
+	bcm96878.dtb
 
 dtb-$(CONFIG_ASPEED_AST2500) += ast2500-evb.dtb
 dtb-$(CONFIG_ASPEED_AST2600) += ast2600-evb.dtb