mtd: fix compile error with musl

Signed-off-by: Felix Fietkau <nbd@openwrt.org>

git-svn-id: svn://svn.openwrt.org/openwrt/trunk@40819 3c298f89-4303-0410-b956-a3cf2f4a3e73
musl: update to version 1.1.1

Signed-off-by: Felix Fietkau <nbd@openwrt.org>

git-svn-id: svn://svn.openwrt.org/openwrt/trunk@40820 3c298f89-4303-0410-b956-a3cf2f4a3e73