atheros CPU feature overrides

w/o override:

root@OpenWrt:/# dmesg | grep ^Memory:
Memory: 12216k/16384k available (1962k kernel code, 4168k reserved, 303k data, 1392k init, 0k highmem)
root@OpenWrt:/# free
              total         used         free       shared      buffers
  Mem:        13608         8108         5500            0            0
 Swap:            0            0            0
Total:        13608         8108         5500
root@OpenWrt:/#

w/ override:

root@OpenWrt:/# dmesg | grep ^Memory:
Memory: 12456k/16384k available (1730k kernel code, 3928k reserved, 303k data, 1384k init, 0k highmem)
root@OpenWrt:/# free
              total         used         free       shared      buffers
  Mem:        13840         8028         5812            0            0
 Swap:            0            0            0
Total:        13840         8028         5812
root@OpenWrt:/#