Compile in the right bits so the AR9130 WMAC support functions correctly.

A previous commit disabled compiling the AR9130 support in the default
HAL build in the kernel. Since the AR9130 support won't actually function
without AH_SUPPORT_AR9130 (and that abomination needs to be undone at some
point, in order to allow USB 11n NICs to also work), we now have to
explicitly compile it in.

But since the 11n RF backends don't (currently) join the RF linker set,
one has to compile in _an_ RF backend for the HAL to compile.