Bump kernel version to 0.280

Change-Id: If58b6c40687bc253e52b3219b7ed7c1d88bacdb6
Use O3 & Linaro for building

This reverts commit 29f01076bd6705e6cc077d3c202f66fda9ed8261.

Change-Id: I479cfa77411f15fc9bfdb9c5411179018c8bb76e
Revert "Revert "arm: Allow CPU-supported unaligned accesses""

This reverts commit 13c5cfe88f20b95ba3d442dd0a0f656db54f9759.
Bump version to 0.281

Change-Id: I2400d42e89ac64c9e95b6f300c265549465e63e5