rpi-base: Add missing hifiberry overlay

There is anoter hifiberry hat, for which there is currently
no overlay added to the build, so let's add it:

hifiberry-dacplusadcpro.dtbo

Signed-off-by: Pascal Huerst <pascal.huerst@gmail.com>

conf/machine/include/rpi-base.inc

@@ -28,6 +28,7 @@ RPI_KERNEL_DEVICETREE_OVERLAYS ?= " \
     overlays/hifiberry-amp.dtbo \
     overlays/hifiberry-dac.dtbo \
     overlays/hifiberry-dacplus.dtbo \
+    overlays/hifiberry-dacplusadcpro.dtbo \
     overlays/hifiberry-digi.dtbo \
     overlays/justboom-both.dtbo \
     overlays/justboom-dac.dtbo \