libc: arcmwdt: grant all threads access to stdio locks

Some of the locks are created in supervisor mode (i.e. stdout one),
but should be accessed from user mode too. Unfortunately, there is
no way to distinguish these locks, so grant the access to all of them
as the actual reads and writes should end up as syscalls anyway.

Signed-off-by: Ilya Tagunov <Ilya.Tagunov@synopsys.com>
(cherry picked from commit e22ca6b1)