vp9: check tile column count

the max is 6. there are assumptions throughout the decode regarding
this; fixes a crash with a fuzzed bitstream

$ zzuf -s 5861 -r 0.01:0.05 -b 6- \
  < vp90-2-00-quantizer-00.webm.ivf \
  | dd of=invalid-vp90-2-00-quantizer-00.webm.ivf.s5861_r01-05_b6-.ivf \
    bs=1 count=81883

Change-Id: I6af41bb34252e88bc156a4c27c80d505d45f5642
diff --git a/test/test.mk b/test/test.mk
index a839723..af344e5 100644
--- a/test/test.mk
+++ b/test/test.mk
@@ -766,6 +766,8 @@
 LIBVPX_TEST_DATA-$(CONFIG_VP9_DECODER) += invalid-vp90-01.webm.res
 LIBVPX_TEST_DATA-$(CONFIG_VP9_DECODER) += invalid-vp90-02.webm
 LIBVPX_TEST_DATA-$(CONFIG_VP9_DECODER) += invalid-vp90-02.webm.res
+LIBVPX_TEST_DATA-$(CONFIG_VP9_DECODER) += invalid-vp90-2-00-quantizer-00.webm.ivf.s5861_r01-05_b6-.ivf
+LIBVPX_TEST_DATA-$(CONFIG_VP9_DECODER) += invalid-vp90-2-00-quantizer-00.webm.ivf.s5861_r01-05_b6-.ivf.res
 
 ifeq ($(CONFIG_DECODE_PERF_TESTS),yes)
 # BBB VP9 streams