dts: stm32wl: Configure LPUART wakeup line

Rather than configuring in serial_wakeup sample, define LPUART1 wakeup
line in wl.dtsi file.

Additionally make few cosmetic changes to nucleo_wl55rj overlay in
serial wakeup sample.

Signed-off-by: Erwan Gouriou <erwan.gouriou@st.com>
2 files changed