Disable creation of multisample images until they work

Change-Id: I39608947651b855c6e2668de98ab5696e18f501f
Reviewed-on: https://swiftshader-review.googlesource.com/c/SwiftShader/+/26310
Tested-by: Chris Forbes <chrisforbes@google.com>
Kokoro-Presubmit: kokoro <noreply+kokoro@google.com>
Reviewed-by: Alexis Hétu <sugoi@google.com>

src/Vulkan/VkImage.cpp

@@ -33,6 +33,11 @@ Image::Image(const VkImageCreateInfo* pCreateInfo, void* mem) :
 	tiling(pCreateInfo->tiling)
 {
 	blitter = new sw::Blitter();
+
+	if (samples != VK_SAMPLE_COUNT_1_BIT)
+	{
+		UNIMPLEMENTED("Multisample images not yet supported");
+	}
 }
 
 void Image::destroy(const VkAllocationCallbacks* pAllocator)