building new kernel fails during build of 'ath' driver

[Fredrik Andersson]

I have the same problem too compile the kernel with ath support .. 
if_ath_pci.o (.text+0xd4):undefined reference to 'ath_hal_probe' 
*** error code 1

My config, FreeBSD 5.2.1-Release on a laptop IBM-A20m.
Hope someone have a good ide why or any solution of the problem .. 
Fred.