[SPARC64]: Fix stack overflow checking in modular non-SMP kernels.

The sparc64 kernel's EXPORT_SYMBOL(_mcount) is inside an
#ifdef CONFIG_SMP. This breaks modules in non-SMP kernels
built with stack overflow checking (CONFIG_STACK_DEBUG=y),
as modules_install reports:

WARNING: /lib/modules/2.6.17/kernel/drivers/ide/ide-cd.ko needs unknown symbol _mcount

Trivially fixed by moving EXPORT_SYMBOL(_mcount) outside of
the #ifdef CONFIG_SMP.

Signed-off-by: Mikael Pettersson <mikpe@it.uu.se>
Signed-off-by: David S. Miller <davem@davemloft.net>