arm: mvebu: Add CRS328-4C-20S-4S board

MikroTik CRS328-4C-20S-4S board has a switch chip with an integrated
Marvell Prestera 98DX3236 CPU.

This commit includes two board variants, namely the factory
default one and a Bit variant. The Bit board variant has a
bigger Macronix flash.

Add basic U-Boot, UART and SPI flash support.

Signed-off-by: Luka Kovacic <luka.kovacic@sartura.hr>
Cc: Luka Perkov <luka.perkov@sartura.hr>
Cc: Jakov Petrina <jakov.petrina@sartura.hr>
Reviewed-by: Stefan Roese <sr@denx.de>
diff --git a/arch/arm/dts/Makefile b/arch/arm/dts/Makefile
index 1eba2b2..8ecf63e 100644
--- a/arch/arm/dts/Makefile
+++ b/arch/arm/dts/Makefile
@@ -222,6 +222,8 @@
 	armada-xp-crs305-1g-4s-bit.dtb		\
 	armada-xp-crs326-24g-2s.dtb		\
 	armada-xp-crs326-24g-2s-bit.dtb		\
+	armada-xp-crs328-4c-20s-4s.dtb		\
+	armada-xp-crs328-4c-20s-4s-bit.dtb	\
 	armada-xp-db-xc3-24g4xg.dtb		\
 	armada-xp-gp.dtb			\
 	armada-xp-maxbcm.dtb			\