Make it clearer what each one means in the comments that define them.
IIC_BUSBSY was used in many places to mean two different things, either
"someone else has reserved the bus so you have to wait until they're done"
or "the signal level on the bus was not in the state I expected before/after
issuing some command".
Now IIC_BUSERR is used consistantly to refer to protocol/signaling errors,
and IIC_BUSBSY refers to ownership/reservation of the bus.
