Revert "makefile: kernel faults with -fschedule-insns2 in GCC 4.8.2"

This reverts commit aa1dc60108c0db1e63840a16d3b6afa1ca0b789d.
Revert "ARM: 7670/1: fix the memset fix"

This reverts commit 956b70cc351ca29a6c882fb615c6de4b27c0f7bd.
Revert "ARM: 7668/1: fix memset-related crashes caused by recent GCC (4.7.2) optimizations"

This reverts commit 826394e37e68da3f16c829ef4ef852a2b4f78db9.
Xens1.5