MVKPhysicalDevice: Get the vendor ID before setting the subgroup size.

At this point in device initialization, the device properties have not
yet been initialized. Unfortunately, this includes the vendor ID, on
which the maximum SIMD-group size depends. Initialize that property so
we can use it to set the subgroup size correctly.

MoltenVK/MoltenVK/GPUObjects/MVKDevice.mm

@@ -1243,6 +1243,7 @@ void MVKPhysicalDevice::initMetalFeatures() {
 #if MVK_MACOS
     if (mvkOSVersionIsAtLeast(10.14)) {
         static const uint32_t kAMDVendorId = 0x1002;
+        initGPUInfoProperties();    // Need to know the vendor ID for this.
         _metalFeatures.subgroupSize = (_properties.vendorID == kAMDVendorId) ? 64 : 32;
     }
 #endif