a) sun4d_boot_one_cpu() should be __cpuinit (called only from
   __cpuinit __cpu_up(), for one thing, leads to calls of __cpuinit
   functions for another).
b) got externs in arch/sparc/kernel/smp.c to match reality.
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>