arm: armv7: temporarily set -mno-unaligned-access

This patch aims at ensuring that the 2012.10 release works
out-of-the-box on as many targets as possible, by reinstating
commit 5347560f5427bcdd48a563b62180481606ac8044, which adds
option -mno-unaligned-access to armv7 builds.

This patch will be overriden immediately after release of 2012.10.