Revert "Kernel build: switch linaro toolchains"

This reverts commit c2a59ffff5b51004cca5ef7e45ce761c4676e77c.
Revert "BoardConfig: Compile kernel with Linaro optimized GCC 4.8 toolchain"

This reverts commit ae92d554e9c10339dac7ecafed29b18403b79c12.