Don't run to comboot API with interrupts off

Don't run to comboot API with interrupts off

We have historically run the comboot API with interrupts off due to
concerns about stack overflow.  However, this is a really bad idea: we
can easily spend a fair bit of time servicing one of these routines,
especially when doing things like waiting for I/O.

In particular, do_idle should *never* be run with interrupts disabled.

Switch to running with interrupts enabled everywhere unless we have
specific reasons not to do so.

Signed-off-by: H. Peter Anvin <hpa@zytor.com>