openrisc: fix the fix of copy_from_user()

commit 8e4b72054f554967827e18be1de0e8122e6efc04 upstream.

Since commit acb2505d0119 ("openrisc: fix copy_from_user()"),
copy_from_user() returns the number of bytes requested, not the
number of bytes not copied.

Cc: Al Viro <viro@zeniv.linux.org.uk>
Fixes: acb2505d0119 ("openrisc: fix copy_from_user()")
Signed-off-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Willy Tarreau <w@1wt.eu>