hdata/test: Remove all temp files

mktemp generates a random file name and creates a blank file with that
name in /tmp. dtdiff_wrap.sh doesn't remove the blank file, or the
re-parsed DTB file so you end up with a lot of them in /tmp.

Signed-off-by: Oliver O'Halloran <oohall@gmail.com>

hdata/test/dtdiff_wrap.sh

@@ -12,5 +12,5 @@ cp /dev/stdin $T.dtb
 dtc -I dts -O dtb $1 > $T.orig.dtb
 dtdiff $T.orig.dtb $T.dtb
 R=$?
-if [ $R == 0 ]; then rm -f $T.dtb; fi
+if [ $R == 0 ]; then rm -f $T $T.orig.dtb $T.dtb; fi
 exit $R