drivers/sensor: lsm6dsv16x: add in DT both INT1 and INT2 pin

Add in DT the possibility to configure both INT1 and INT2
pin. The driver will then assign one of the two (either 1
or 2, according to what value drdy_pin is set) to a gpio
for receiving drdy interrupts.

The other pin may be used in the future to receive event
interrupts.

Signed-off-by: Armando Visconti <armando.visconti@st.com>