Fix createBuffer in Vulkan

TBR=bsalomon@google.com

BUG=skia:
GOLD_TRYBOT_URL= https://gold.skia.org/search2?unt=true&query=source_type%3Dgm&master=false&issue=1897373002

Review URL: https://codereview.chromium.org/1897373002
diff --git a/src/gpu/vk/GrVkGpu.cpp b/src/gpu/vk/GrVkGpu.cpp
index b23cced..5fba475 100644
--- a/src/gpu/vk/GrVkGpu.cpp
+++ b/src/gpu/vk/GrVkGpu.cpp
@@ -180,16 +180,20 @@
             SkASSERT(kDynamic_GrAccessPattern == accessPattern ||
                      kStatic_GrAccessPattern == accessPattern);
             buff = GrVkVertexBuffer::Create(this, size, kDynamic_GrAccessPattern == accessPattern);
+            break;
         case kIndex_GrBufferType:
             SkASSERT(kDynamic_GrAccessPattern == accessPattern ||
                      kStatic_GrAccessPattern == accessPattern);
             buff = GrVkIndexBuffer::Create(this, size, kDynamic_GrAccessPattern == accessPattern);
+            break;
         case kXferCpuToGpu_GrBufferType:
             SkASSERT(kStream_GrAccessPattern == accessPattern);
             buff = GrVkTransferBuffer::Create(this, size, GrVkBuffer::kCopyRead_Type);
+            break;
         case kXferGpuToCpu_GrBufferType:
             SkASSERT(kStream_GrAccessPattern == accessPattern);
             buff = GrVkTransferBuffer::Create(this, size, GrVkBuffer::kCopyWrite_Type);
+            break;
         default:
             SkFAIL("Unknown buffer type.");
             return nullptr;