u-boot-tools: add the fdt_add_pubkey script to the list of files to be shipped

This commit fixes a build issue when this script is installed but not shipped
in the u-boot-tools package.

Signed-off-by: Arturo Buzarra <arturo.buzarra@digi.com>

meta-digi-arm/recipes-bsp/u-boot/u-boot-tools_%.bbappend

@@ -18,4 +18,7 @@ do_install:append () {
 	fi
 }
 
-FILES:${PN}-mkimage += "${bindir}/uboot-fdt_add_pubkey"
+FILES:${PN}-mkimage += " \
+	${bindir}/uboot-fdt_add_pubkey \
+	${bindir}/fdt_add_pubkey \
+"