Export __kernel_thread so we can load nfs as a module.

--- ./arch/ppc/kernel/ppc_ksyms.c.DIST	Fri May 31 16:28:12 2002
+++ ./arch/ppc/kernel/ppc_ksyms.c	Sun Nov 10 10:31:15 2002
@@ -59,6 +59,8 @@
 EXPORT_SYMBOL(ip_fast_csum);
 EXPORT_SYMBOL(csum_tcpudp_magic);
 
+extern long __kernel_thread(unsigned long, int (*)(void *), void *);
+EXPORT_SYMBOL(__kernel_thread);
 
 EXPORT_SYMBOL(__copy_tofrom_user);
 EXPORT_SYMBOL(__clear_user);