Add support of coredump with CM4

Signed-off-by: Christophe Priouzeau <christophe.priouzeau@st.com>

recipes-extended/m4coredump/files/85-m4-dump.rules

@@ -0,0 +1 @@
+SUBSYSTEM=="devcoredump", ACTION=="add", RUN+="#BINDIR#/stm32mp-m4fwdump.sh"

recipes-extended/m4coredump/files/stm32mp-m4fwdump.sh

@@ -0,0 +1,7 @@
+#!/bin/sh
+
+mkdir -p /var/crash
+timestamp=$(date +%F_%H-%M-%S)
+filename=/var/crash/m4-fw-error_${timestamp}.dump
+cat /sys/${DEVPATH}/data > ${filename}
+echo 1 > /sys/${DEVPATH}/data