improve dmesg output to help with debugging.

improve dmesg output to help with debugging.

for SoCs that can provide multiple instances of rkclock, let them
provide a name that will be printed during attach so you can tell
which one is doing what.

when rkclock_set_frequency isn't handling a clock, have it print
which rkclock instance isn't handling a clock. while here, print
the clock index the same way the #define refers to them.

ok kettenis@