dts: arm: st: added sensor aliases

Added aliases to nucleo_l4r5zi/stm32f4_disco/stm32f411e_disco for
die_temp die_temp/vref/vbat nodes so that the die_temp_polling
and soc_voltage samples work for them.

Signed-off-by: Yishai Jaffe <yishai1999@gmail.com>