[toolchain] musl: backport an upstream fix for MIPS and termios constants

Fixes weird console behavior with a musl rootfs.

Signed-off-by: Florian Fainelli <florian@openwrt.org>

git-svn-id: svn://svn.openwrt.org/openwrt/trunk@34318 3c298f89-4303-0410-b956-a3cf2f4a3e73