fix other printf warning for SkBlendMode

BUG=skia:
GOLD_TRYBOT_URL= https://gold.skia.org/search?issue=2393253003

Review-Url: https://codereview.chromium.org/2393253003
diff --git a/src/utils/SkDumpCanvas.cpp b/src/utils/SkDumpCanvas.cpp
index eda23b7..eb56068 100644
--- a/src/utils/SkDumpCanvas.cpp
+++ b/src/utils/SkDumpCanvas.cpp
@@ -541,7 +541,7 @@
     if (p) {
         msg.appendf(" color:0x%08X flags:%X", p->getColor(), p->getFlags());
         if (!p->isSrcOver()) {
-            msg.appendf(" blendmode:%d", p->getBlendMode());
+            msg.appendf(" blendmode:%d", (int)p->getBlendMode());
         }
         appendFlattenable(&msg, p->getShader(), "shader");
         appendFlattenable(&msg, p->getPathEffect(), "pathEffect");