per-revision reg values (style question)

[coypu%SDF.ORG@localhost]

I'm trying to make athn(4) work for my newer AR9485 (support ends at
92xx now)
driver originally comes from linux and was written by Atheros.

in linux code they have a lot of quirks that we do not have. I think I
should update all of sys/dev/ic/athnreg.h accordingly.

there are many regs that vary by revision, e.g.
drivers/net/wireless/ath/ath9k/reg.h:23

#define AR_CR_RXE            (AR_SREV_9300_20_OR_LATER(ah) ? 0x0000000c : 0x00000004)

whereas for us (we do not have 9300 or later support)

#define AR_CR_RXE            0x00000004


I think whenever we have something like this we turn it into a function.
should I turn every single one of those cases to AR_CR_RXE(sc) ... and
change the code of the driver accordingly?

thanks.