kirkwood: Add support for Sheevaplug

kirkwood: Add support for Sheevaplug

Globalscale SheevaPlug:
* Marvell Kirkwood 88F6281
* 512 MB SDRAM
* 512 MB Flash
* Gigabit Network
* USB 2.0
* SD slot
* Serial console

The device is supported in mainline uboot/linux the commit adds only
some openwrt config for building an image.

Installation:
1 - Update uboot:
setenv ipaddr '192.168.0.111'
setenv serverip '192.168.0.1'
tftpboot u-boot.kwb
nand erase 0x0 0x100000
nand write 0x800000 0x0 0x100000
reset
2 - Install OpenWRT:
setenv ethaddr 00:50:43:01:xx:xx
saveenv
setenv ipaddr '192.168.0.111'
setenv serverip '192.168.0.1'
tftpboot openwrt-kirkwood-globalscale_sheevaplug-squashfs-factory.bin
nand erase.part ubi
nand write 0x800000 ubi 0x600000
reset

Signed-off-by: BERENYI Balazs <balazs@wee.hu>
Reviewed-by: Pawel Dembicki <paweldembicki@gmail.com>
[add vendor name for uboot-kirkwood, merge patches, copy to 5.10,
add AUTORELEASE for uboot-kirkwood, refresh patches]
Signed-off-by: Adrian Schmutzler <freifunk@adrianschmutzler.de>