boards: stm32h747i_disco: Minor fixes

* Exlude _m4target from net tests as they assume SERIAL is enabled,
which is not the case (yet).
Fixes: #19065
* Zephyr drivers headers were moved from include/ to include/drivers.
Update pinmux.h path to the new location.
* Add missing status line on joystick_left dts node.

Signed-off-by: Erwan Gouriou <erwan.gouriou@linaro.org>