ath9k: make ATH_SREV macros more consistent

This makes the macros more consistent and removes hidden dependencies on
ah for macros that take _ah as a parameter.

This change does not appear to affect the final binary.

Signed-off-by: Wenli Looi <wlooi@ucalgary.ca>
Acked-by: Toke Høiland-Jørgensen <toke@toke.dk>
Signed-off-by: Kalle Valo <quic_kvalo@quicinc.com>
Link: https://lore.kernel.org/r/20220320233010.123106-2-wlooi@ucalgary.ca