uboot-envtool: remove superfluous + sign from PKG_BUILD_DEPENDS

A + sign does not have meaning in build depends.

Signed-off-by: Matthias Schiffer <mschiffer@universe-factory.net>

package/boot/uboot-envtools/Makefile

@@ -19,7 +19,7 @@ PKG_SOURCE_URL:=\
 	ftp://ftp.denx.de/pub/u-boot
 PKG_HASH:=bdc68d5f9455ad933b059c735d983f2c8b6b552dafb062e5ff1444f623021955
 
-PKG_BUILD_DEPENDS:=+fstools
+PKG_BUILD_DEPENDS:=fstools
 
 PKG_LICENSE:=GPL-2.0 GPL-2.0+
 PKG_LICENSE_FILES:=Licenses/README