powerpc: switch to generic fork/clone/vfork

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
diff --git a/arch/powerpc/Kconfig b/arch/powerpc/Kconfig
index 5af5aa7..951a517 100644
--- a/arch/powerpc/Kconfig
+++ b/arch/powerpc/Kconfig
@@ -145,6 +145,7 @@
 	select HAVE_MOD_ARCH_SPECIFIC
 	select MODULES_USE_ELF_RELA
 	select GENERIC_KERNEL_EXECVE
+	select CLONE_BACKWARDS
 
 config EARLY_PRINTK
 	bool