vfs: usb_serial_jtag: consider O_NONBLOCK flag when reading via driver
vfs: usb_serial_jtag: consider O_NONBLOCK flag when reading via driver

Closes https://github.com/espressif/esp-idf/issues/8839

espressif/esp-idf,espressif/esp-idf,espressif/esp-idf,espressif/esp-idf