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 d762746 ("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>

arch/um/kernel/exec.c

@@ -62,7 +62,7 @@ static long execve1(const char *file,
 	return error;
 }
 
-long um_execve(const char *file, char __user *__user *argv, char __user *__user *env)
+long um_execve(const char *file, const char __user *const __user *argv, const char __user *const __user *env)
 {
 	long err;
 
@@ -72,8 +72,8 @@ long um_execve(const char *file, char __user *__user *argv, char __user *__user
 	return err;
 }
 
-long sys_execve(const char __user *file, char __user *__user *argv,
-		char __user *__user *env)
+long sys_execve(const char __user *file, const char __user *const __user *argv,
+		const char __user *const __user *env)
 {
 	long error;
 	char *filename;

arch/um/kernel/internal.h

@@ -1 +1 @@
-extern long um_execve(const char *file, char __user *__user *argv, char __user *__user *env);
+extern long um_execve(const char *file, const char __user *const __user *argv, const char __user *const __user *env);

arch/um/kernel/syscall.c

@@ -60,8 +60,8 @@ int kernel_execve(const char *filename,
 
 	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;