The _open() C function is declared as having variable arguments in
newlib, so second and third arguments are passed on stack. Add code to
move them into registers, since that's where the PRU simulator expects
them.
Issue was exposed by the GCC test gcc.c-torture/execute/fprintf-2.c,
which relies on tmpnam implementation to pass correct flags to _open.
Signed-off-by: Dimitar Dimitrov <dimitar@dinux.eu>
21f0edbf9f