pmac_zilog: initialize the serial ports' spinlocks even if console over 
   serial is not enabled; disable this driver by default for ppc

This lock not being initialized was Oopsing my TiBook :-P
Signed-off-by: David Eger <eger@havoc.gtf.org>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>