Don't set vk sampler on desc set if using immutable samplers.

This appeases a validation layer error. Its unclear if the validation
is correct saying this was an error before (since sampler param isn't
used when we have immutable samplers), but this isn't wrong either and
makes the layers not complain.

Change-Id: I88e8017df203965af0030b153ff933384a6215d6
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/324698
Commit-Queue: Greg Daniel <egdaniel@google.com>
Auto-Submit: Greg Daniel <egdaniel@google.com>
Reviewed-by: Jim Van Verth <jvanverth@google.com>

Author: egdaniel

src/gpu/vk/GrVkPipelineState.cpp

@@ -177,7 +177,7 @@ bool GrVkPipelineState::setAndBindTextures(GrVkGpu* gpu,
 
             VkDescriptorImageInfo imageInfo;
             memset(&imageInfo, 0, sizeof(VkDescriptorImageInfo));
-            imageInfo.sampler = sampler->sampler();
+            imageInfo.sampler = fImmutableSamplers[i] ? VK_NULL_HANDLE : sampler->sampler();
             imageInfo.imageView = textureView->imageView();
             imageInfo.imageLayout = VK_IMAGE_LAYOUT_SHADER_READ_ONLY_OPTIMAL;