uml: fix compile warning

This fixes:
incompatible pointer type:  => 89
       arch/um/kernel/exec.c: warning: passing argument 2 of 'execve1' from
incompatible pointer type:  => 69, 85
       arch/um/kernel/exec.c: warning: passing argument 3 of 'execve1' from
incompatible pointer type:  => 69, 85

which was introduced by d7627467b7a8d ("Make do_execve() take a const
filename pointer")

Signed-off-by: Richard Weinberger <richard@nod.at>
Cc: David Howells <dhowells@redhat.com>
Cc: Jeff Dike <jdike@addtoit.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/arch/um/kernel/syscall.c b/arch/um/kernel/syscall.c
index 5ddb246..f958cb8 100644
--- a/arch/um/kernel/syscall.c
+++ b/arch/um/kernel/syscall.c
@@ -60,8 +60,8 @@
 
 	fs = get_fs();
 	set_fs(KERNEL_DS);
-	ret = um_execve(filename, (char __user *__user *)argv,
-			(char __user *__user *) envp);
+	ret = um_execve(filename, (const char __user *const __user *)argv,
+			(const char __user *const __user *) envp);
 	set_fs(fs);
 
 	return ret;