Fix vulkan resolve

BUG=skia:
GOLD_TRYBOT_URL= https://gold.skia.org/search?issue=2215353003

Review-Url: https://codereview.chromium.org/2215353003
diff --git a/src/gpu/vk/GrVkGpu.cpp b/src/gpu/vk/GrVkGpu.cpp
index 8e20444..85bfce8 100644
--- a/src/gpu/vk/GrVkGpu.cpp
+++ b/src/gpu/vk/GrVkGpu.cpp
@@ -366,9 +366,7 @@
 }
 
 void GrVkGpu::onResolveRenderTarget(GrRenderTarget* target) {
-    if (target->needsResolve()) {
-        SkASSERT(target->numColorSamples() > 1);
-
+    if (target->needsResolve() && target->numColorSamples() > 1) {
         GrVkRenderTarget* rt = static_cast<GrVkRenderTarget*>(target);
         SkASSERT(rt->msaaImage());