Advertise variableMultisampleRate feature

We use the sample count from the pipeline in all cases, so we don't have
to do anything special for this.

Bug: b/146387550
Change-Id: I1f1fd33a257bcb9d528efef94d0c919a42d56400
Reviewed-on: https://swiftshader-review.googlesource.com/c/SwiftShader/+/39608
Tested-by: Chris Forbes <chrisforbes@google.com>
Kokoro-Presubmit: kokoro <noreply+kokoro@google.com>
Reviewed-by: Nicolas Capens <nicolascapens@google.com>

src/Vulkan/VkPhysicalDevice.cpp

diff --git a/src/Vulkan/VkPhysicalDevice.cpp b/src/Vulkan/VkPhysicalDevice.cpp
index 164a12f..14b608e 100644
--- a/src/Vulkan/VkPhysicalDevice.cpp
+++ b/src/Vulkan/VkPhysicalDevice.cpp
@@ -98,7 +98,7 @@
 		VK_FALSE,  // sparseResidency8Samples
 		VK_FALSE,  // sparseResidency16Samples
 		VK_FALSE,  // sparseResidencyAliased
-		VK_FALSE,  // variableMultisampleRate
+		VK_TRUE,   // variableMultisampleRate
 		VK_FALSE,  // inheritedQueries
 	};