ath6kl: cleanup diagnose window read and write functions

Just to make them a bit easier to read and unify naming. 32 suffix
in the function name means that it will be a 32 bit transfer. If there's
no number a buffer is transfered instead.

Use void pointers to get rid of ugly casts.

Don't provide target address as a pointer, pass it by value. Same for
the value used in write32().

Signed-off-by: Kalle Valo <kvalo@qca.qualcomm.com>