Update Coral SVN to 31

Bug: 173545603
Change-Id: Ib2f86b48c7bccb4a870384c13756ac4636fc20cf
(cherry picked from commit 06426d0a7cd7491dd258f2fb14aa90ef1c0e97df)
diff --git a/device.mk b/device.mk
index d6546ea..05c77d8 100644
--- a/device.mk
+++ b/device.mk
@@ -967,7 +967,7 @@
 
 # Increment the SVN for any official public releases
 PRODUCT_PROPERTY_OVERRIDES += \
-	ro.vendor.build.svn=30
+	ro.vendor.build.svn=31
 
 PRODUCT_COPY_FILES += \
     $(LOCAL_PATH)/powerhint.json:$(TARGET_COPY_OUT_VENDOR)/etc/powerhint.json