Revert "Switch to Linaro 4.7.3"

This reverts commit d569442985da9f04e9a7749b30cba4d1b6cf4034.
Revert "Switch to Linaro 4.6"

This reverts commit b37c627cfb85e2dde1e5e7c1b85362c6bec3c521.
Revert "Switch to Add Cortex-A8 optimized Linaro 4.7.3 (2013-03) prebuilt toolchain and build with -O3"

This reverts commit 9e12121c1876246842cb3af2062d6ac70894f65d.