bootstd: Require HUSH_PARSER for script booting

Armbian uses a script which needs the HUSH parser. It is likely that
other distros will do the same. Enable it by default, just in case.

Signed-off-by: Simon Glass <sjg@chromium.org>
Tested-by: Jonas Karlman <jonas@kwiboo.se>
diff --git a/boot/Kconfig b/boot/Kconfig
index 8c27f52..9882812 100644
--- a/boot/Kconfig
+++ b/boot/Kconfig
@@ -638,6 +638,7 @@
 config BOOTMETH_SCRIPT
 	bool "Bootdev support for U-Boot scripts"
 	default y if BOOTSTD_FULL
+	select HUSH_PARSER
 	help
 	  Enables support for booting a distro via a U-Boot script. This makes
 	  the bootdevs look for a 'boot/boot.scr' file which can be used to