au1000: make sysupgrade compatible with all file system types

This patch adds support for all file system types as discussed earlier:

https://lists.openwrt.org/pipermail/openwrt-devel/2013-October/022109.html

This patch depends on a previous patch:

https://lists.openwrt.org/pipermail/openwrt-devel/2013-October/022111.html



Signed-off-by: Philipp Borgers <borgers@mi.fu-berlin.de>

SVN-Revision: 38675