Remove struct ath_pci_softc, it's pointless for supported kernels

aps_pmstate is not used, so struct ath_pci_softc is equivalent to struct
ath_softc.
Remove struct ath_ahb_softc, it's pointless for supported kernels

aps_pmstate is not used, so struct ath_ahb_softc is equivalent to struct
ath_softc.