Address rpardini review round 2: major cleanup

- Use SERIALCON instead of systemd override for serial console
- Remove fdtfile from bootenv (use BOOT_FDT_FILE instead)
- Remove ATF_COMPILER (arm64 default)
- Inline OPTEE variables into fetch_sources_tools hook
- Remove empty family_tweaks() and family_tweaks_bsp()
- Use only debug mode for ATF build
- Build fiptool in atf_custom_postprocess
- Move header creation inline into uboot_custom_postprocess
- Use <<- heredoc for Python script

Author: TuAFBogey

config/boards/numaker-iot-ma35d16f90.csc

@@ -11,20 +11,7 @@ BOOT_FDT_FILE="nuvoton/ma35d1-iot-512m.dtb"
 BOOT_SCENARIO="blobless"
 IMAGE_PARTITION_TABLE="msdos"
 DEFAULT_CONSOLE="serial"
+SERIALCON="ttyS0:115200"
 
 # Hardware features
 HAS_VIDEO_OUTPUT="yes"
-
-function post_family_tweaks__numaker_iot_ma35d16f90() {
-	display_alert "$BOARD" "Applying NuMaker IoT MA35D16F90 tweaks" "info"
-
-	# Serial console 115200 baud
-	mkdir -p "$SDCARD/etc/systemd/system/[email protected]/"
-	cat <<- EOF > "$SDCARD/etc/systemd/system/[email protected]/override.conf"
-		[Service]
-		ExecStart=
-		ExecStart=-/sbin/agetty -o '-p -- \\u' 115200 ttyS0 linux
-	EOF
-
-	return 0
-}

config/bootenv/nuvoton-ma35d1.txt

@@ -1,3 +1,2 @@
 bootlogo=false
 console=serial
-fdtfile=nuvoton/ma35d1-iot-512m.dtb