malta: restore "be" subtarget from being source-only

The malta "be" and "le" subtargets share the arch with many devices of
ar71xx and ramips.  They can be handy for testing, debugging, trying
both snapshot and release builds.

This commit makes the "be" subtarget part of the ci and release builds

Signed-off-by: Yousong Zhou <yszhou4tech@gmail.com>

target/linux/malta/Makefile

@@ -12,7 +12,7 @@ CPU_TYPE:=24kc
 SUBTARGETS:=le be le64 be64
 INITRAMFS_EXTRA_FILES:=
 MAINTAINER:=Florian Fainelli <florian@openwrt.org>
-FEATURES:=ramdisk source-only
+FEATURES:=ramdisk
 
 KERNEL_PATCHVER:=4.4
 

target/linux/malta/be64/target.mk

@@ -1,6 +1,7 @@
 ARCH:=mips64
 CPU_TYPE:=mips64
 SUBTARGET:=be64
+FEATURES+=source-only
 BOARDNAME:=Big Endian (64-bits)
 
 define Target/Description

target/linux/malta/le/target.mk

@@ -1,5 +1,6 @@
 ARCH:=mipsel
 SUBTARGET:=le
+FEATURES+=source-only
 BOARDNAME:=Little Endian
 
 define Target/Description

target/linux/malta/le64/target.mk

@@ -1,6 +1,7 @@
 ARCH:=mips64el
 CPU_TYPE:=mips64
 SUBTARGET:=le64
+FEATURES+=source-only
 BOARDNAME:=Little Endian (64-bits)
 
 define Target/Description