vulkan: Temporarily hack around loader/driver mismatch

A driver was built with an older declaration of
vkGetSwapchainGrallocUsage2KHR, and doesn't match what libvulkan
expects. This is a temporary workaround until the driver can be
rebuilt against the current header. When a new driver is available,
this change should be reverted.

Test: vulkanGears on affected device
Change-Id: I5a8bb16f0f9563e32314cff2a2a7a45760cfc356
diff --git a/vulkan/libvulkan/driver.h b/vulkan/libvulkan/driver.h
index e058439..5383f59 100644
--- a/vulkan/libvulkan/driver.h
+++ b/vulkan/libvulkan/driver.h
@@ -102,6 +102,7 @@
 
     VkDevice driver_device;
     DeviceDriverTable driver;
+    uint32_t driver_version;
 };
 
 bool Debuggable();