arm: mvebu: Add CRS305-1G-4S board

CRS305-1G-4S has a switch chip with an integrated CPU (98DX3236) and
like some of the other similar boards requires bin_hdr.
bin_hdr (DDR3 init stage) is currently retrieved from the stock
bootloader and compiled into the kwb image.

Adds support for U-Boot, enable UART, SPI, Winbond SPI flash chip
support and writing env to SPI flash.

Signed-off-by: Luka Kovacic <me@lukakovacic.xyz>
Reviewed-by: Chris Packham <judge.packham@gmail.com>
Reviewed-by: Stefan Roese <sr@denx.de>
Signed-off-by: Stefan Roese <sr@denx.de>
diff --git a/board/mikrotik/crs305-1g-4s/MAINTAINERS b/board/mikrotik/crs305-1g-4s/MAINTAINERS
new file mode 100644
index 0000000..3823489
--- /dev/null
+++ b/board/mikrotik/crs305-1g-4s/MAINTAINERS
@@ -0,0 +1,7 @@
+CRS305-1G-4S BOARD
+M:	Luka Kovacic <me@lukakovacic.xyz>
+S:	Maintained
+F:	board/mikrotik/crs305-1g-4s/
+F:	include/configs/crs305-1g-4s.h
+F:	configs/crs305-1g-4s_defconfig
+F:	arch/arm/dts/armada-xp-crs305-1g-4s.dts