stty: fix open and read calls
Summary
This merge request fixes the open() and read() calls for tty devices on rtems tester and run.
Opening a device in 'rw' mode causes:
error: opening tty dev: /dev/ttyACM0: must have exactly one of create/read/write/append mode
Reading from device:
Exception in thread tty[/dev/ttyACM0]:
[...]
File "/usr/lib/python3.10/codecs.py", line 321, in decode
data = self.buffer + input
TypeError: can't concat NoneType to bytes
Edited by Ranulfo Raphael