arm-rpi4: Use /boot/efi as bootmountpoint

Also added download support on the Raspberry Pi 3.
The following feature has appeared. The FAT partition does not
install the last installed kernel, but the first kernel in the
KFLAVOURS list. This was done in order to enable  u-boot to
default load another kernel, for example std-def.

features.in/arm-rpi4/image-scripts.d/98-bootstrap-boot-by-firmware

@@ -1,3 +1,43 @@
-#!/bin/sh -efu
+#!/bin/sh -eu
 
-rpi4-boot-nouboot --bootstrap
+kflavour=
+kflavour="${GLOBAL_KFLAVOURS%% *}"
+
+mkdir -p /boot/efi
+
+uboots="rpi_3 rpi_3_32b rpi_4 rpi_4_32b"
+for uboot in $uboots; do
+	[ -d /usr/share/u-boot/$uboot ] &&
+	  cp -f /usr/share/u-boot/$uboot/* /boot/efi/
+	[ -f /boot/efi/kernel8.img ] &&
+	  mv /boot/efi/{kernel8.img,uboot-$uboot.bin}
+	[ -f /boot/efi/kernel7.img ] &&
+	  mv /boot/efi/{kernel7.img,uboot-$uboot.bin}
+done
+
+rm -f /boot/efi/config.txt
+
+[ "$GLOBAL_ARCH" = aarch64 ] && \
+	echo "arm_64bit=1" > /boot/efi/config.txt
+
+cat >> /boot/efi/config.txt <<EOF
+enable_uart=1
+disable_overscan=1
+dtparam=audio=on
+
+[pi3]
+kernel=uboot-rpi_3.bin
+dtoverlay=vc4-kms-v3d
+
+[pi4]
+kernel=uboot-rpi_4.bin
+dtoverlay=vc4-fkms-v3d
+
+[all]
+EOF
+
+[ "$GLOBAL_ARCH" = armh ] && \
+	sed -i 's/.bin/-32b.bin/g' /boot/efi/config.txt
+
+# Enable bootloading without u-boot
+sh -x rpi4-boot-nouboot $kflavour