[patch] prevent atkbd(4) from calling callback in polled mode

hello,

would anyone object to the small attached atkbd(4) patch? the idea is
to basically prevent atkbd(4) interrupt handler from calling keyboard
callback function when polled mode is enabled.

i would really like to hear from people who is using kbdmux(4) on smp
systems and having problems with duplicated/missing characters while
using keyboard at mountroot, geli, etc. prompts. basically, when low
level console input functions (cngetc(), gets(), etc.) are used _and_
interrupts are enabled.

thanks,
max