Add helper to fetch imx firmware

debian/bin/fetch-imx-firmware

+#!/bin/bash
+
+set -e
+
+URL_BASE=https://www.nxp.com/lgfiles/NMG/MAD/YOCTO/
+FIRMWARE=firmware-imx-8.7.bin
+
+function cleanup()
+{
+  [ -z "${DLDIR}" ] || rm -rf "${DLDIR}"
+}
+
+trap cleanup EXIT
+
+if [ -z "$1" ]; then
+    echo "No output dir given" 1>&2
+    exit 1
+fi
+
+OUT=$1
+DLDIR=$(mktemp -d)
+cd "${DLDIR}"
+wget "${URL_BASE}/${FIRMWARE}"
+chmod +x "${FIRMWARE}"
+./"${FIRMWARE}" --auto-accept
+cd -
+
+for f in ddr/synopsys/lpddr4_pmu_train_?d_?mem.bin hdmi/cadence/signed_*_imx8m.bin; do
+	cp -v ${DLDIR}/$(basename "${FIRMWARE}" .bin)/firmware/$f "${OUT}"
+done