[Sound-open-firmware] Headers circular dependency

[Paul Olaru]

As I was trying to turn the main macros (spin_lock, spin_lock_irq and the others) from
<spinlock.h> I have uncovered the fact that <sof/spinlock.h> includes <sof/drivers/interrupt.h>
and <sof/drivers/interrupt.h> includes <sof/spinlock.h>, which means that for every C file
that includes either of them one of the two will not see the declarations of the other.

Is this circular dependency actually real?

Right now I have issues with interrupt_global_disable - it does an implicit declaration in
<spinlock.h> due to <interrupt.h> being included first (or only) within some C files.

If I try to include <arch/spinlock.h> from <sof/interrupt.h> I only get the error for
"this file shouldn't be included from outside of sof/spinlock.h", but if I try to hack
it to believe it's from there I get no further errors.

I will submit a pull request displaying that soon (hopefully today) but I need feedback
on whether this is the best approach. I mean the cyclic dependency is real because
<sof/interrupt.h> needs to use spinlock_t but <sof/spinlock.h> requires several things
from <sof/interrupt.h> so I believe it needs to be fixed even if the macros from
<sof/spinlock.h> are left as macros.