Add basic support for stm32h743i-discovery board

This board offers :
  _ 2MBytes Flash
  _ 1 x micro USB OTG port
  _ 1 x STLink connector (micro USB)
  _ 1 x micro SD card slot
  _ 1 x RJ45 connector
  _ 1 x RCA connector
  _ 2 x Audio jack connectors (in and out)
  _ 2 x speaker connectors (left and right)
  _ 1 x joystick
  _ 1 x DCMI connector (Digital camera interface)
  _ 1 x 4 inch DSI LCD (Display Serial Interface)
  _ Arduino Uno Connectors
  _ 2 x PIO connectors (PMOD and PMOD+)
  _ 1 x wakeup button
  _ 1 x reset button

Signed-off-by: Patrice Chotard <patrice.chotard@st.com>
Signed-off-by: Alexandre TORGUE <alexandre.torgue@st.com>