x86, um: convert to saner kernel_execve() semantics

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index d93eb9d..45edcba 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -98,6 +98,7 @@
 	select GENERIC_STRNCPY_FROM_USER
 	select GENERIC_STRNLEN_USER
 	select GENERIC_KERNEL_THREAD
+	select GENERIC_KERNEL_EXECVE
 
 config INSTRUCTION_DECODER
 	def_bool (KPROBES || PERF_EVENTS || UPROBES)