um: switch to generic kernel_thread()

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
diff --git a/arch/x86/um/Kconfig b/arch/x86/um/Kconfig
index 9926e11..da85b6f 100644
--- a/arch/x86/um/Kconfig
+++ b/arch/x86/um/Kconfig
@@ -13,6 +13,7 @@
 config UML_X86
 	def_bool y
 	select GENERIC_FIND_FIRST_BIT
+	select GENERIC_KERNEL_THREAD
 
 config 64BIT
 	bool "64-bit kernel" if SUBARCH = "x86"