Since I have been looking in to the lcoking issues recently
the following rather trivial gabrage code collection became
obvious...

 - Remove "not yet used" code from 1995 in asm/locks.h. It's garbage.

 - Remove useless DEBUG_SPINLOCK code from generic spinlock.h code. Just
   compiling for SMP does the trick already.

 - Replace all usages of SPINLOCK_DEBUG with the now global
   CONFIG_DEBUG_SPINLOCK.