ARM: dts: stm32: fix RCC node name on stm32f429 MCU

This prevent warning observed with "make dtbs_check W=1"

Warning (simple_bus_reg): /soc/rcc@40023810: simple-bus unit address format
error, expected "40023800"

Signed-off-by: Alexandre Torgue <alexandre.torgue@foss.st.com>