[toolchain] gcc-linaro-4.7: update to 2012.12

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

git-svn-id: svn://svn.openwrt.org/openwrt/trunk@35043 3c298f89-4303-0410-b956-a3cf2f4a3e73