arm: add initial support for the Phytium Pomelo Board

This adds platform code and the device tree for the Phytium Pomelo Board.
The initial support comprises the UART and the PCIE.

Signed-off-by: weichangzheng <nicholas_zheng@outlook.com>
diff --git a/arch/arm/dts/Makefile b/arch/arm/dts/Makefile
index e53ad53..56ed7b6 100644
--- a/arch/arm/dts/Makefile
+++ b/arch/arm/dts/Makefile
@@ -1188,6 +1188,7 @@
 dtb-$(CONFIG_TARGET_TOTAL_COMPUTE) += total_compute.dtb
 
 dtb-$(CONFIG_TARGET_DURIAN) += phytium-durian.dtb
+dtb-$(CONFIG_TARGET_POMELO) += phytium-pomelo.dtb
 
 dtb-$(CONFIG_TARGET_PRESIDIO_ASIC) += ca-presidio-engboard.dtb