kernel: replace local m25p80 patches with upstream submission

http://lists.infradead.org/pipermail/linux-mtd/2013-August/048154.html
http://patchwork.ozlabs.org/patch/268019/

Signed-off-by: Luka Perkov <luka@openwrt.org>

git-svn-id: svn://svn.openwrt.org/openwrt@37808 3c298f89-4303-0410-b956-a3cf2f4a3e73