apm821xx: fix MBL DUO SUPPORTED_DEVICES compat id

The MyBook Live DUO used "wd,mybooklive-duo" as the first
compatible string and not "wd_mybooklive-duo".

Fixes: 9b47aa93c7 ("apm821xx: unify My Book Live Single + Duo images")
Signed-off-by: Christian Lamparter <chunkeey@gmail.com>

target/linux/apm821xx/image/Makefile

@@ -224,7 +224,7 @@ define Device/wd_mybooklive
   DEVICE_TITLE := Western Digital My Book Live Series (Single + Duo)
   DEVICE_PACKAGES := kmod-usb-dwc2 kmod-usb-ledtrig-usbport kmod-usb-storage kmod-fs-vfat wpad-basic
   DEVICE_DTS := wd-mybooklive
-  SUPPORTED_DEVICES += mbl wd_mybooklive-duo
+  SUPPORTED_DEVICES += mbl wd,mybooklive-duo
   BLOCKSIZE := 1k
   DTB_SIZE := 16384
   KERNEL := kernel-bin | dtb | gzip | uImage gzip