pitx-imx8m: add update to distro_boot boot_scripts

- use the 'update_pitx/update.scr' script for bootloader updates in
  emmc boot partition 0.
Signed-off-by: Thomas Schaefer <thomas.schaefer@kontron.com>

include/configs/pitx-imx8m.h

@@ -165,6 +165,7 @@
 		"run loadimage && " \
 		"run loadfdt && " \
 		"booti ${loadaddr} - ${fdt_addr_r} || false\0" 			\
+	"boot_scripts=boot.scr.uimg boot.scr update_pitx/update.scr\0"		\
 	"loadimage=load ${intf} ${bdev}:${bpart} ${loadaddr} ${image}\0" 	\
 	"loadfdt=run set_fdtfile && " \
 		"load ${intf} ${bdev}:${bpart} ${fdt_addr_r} ${fdtfile}\0" 	\