Change handling for SPL based images (#578)

* Change handling for SPL based images

* Fix script

* Fix path for rauc-hook

Documentation/development.md

@@ -5,7 +5,6 @@
 `BOOT_SYS`:
 - efi
 - hyprid
-- spl
 - mbr
 
 HassOS is basicly used GPT. But for use GPT we need own the first 1024 of
@@ -13,6 +12,12 @@ boot drive. Is that not possible, you can use MBR for your device, they work als
 
 Hyprid and SPL use both a hyprid MBR/GPT table but SPL move the GPT header 8MB for give space to write SPL and boot images before.
 
+`BOOT_SPL`:
+- true
+- false
+
+Enable SPL update handling.
+
 `BOOTLOADER`:
 - uboot
 - barebox