A mistake found its way into the previous "Provoking vertex fixes"
cl. This cl fixes the vkGetPhysicalDeviceFeatures2 function for the
VK_EXT_provoking_vertex extension.

Bug: angleproject:3677, angleproject:3430
Change-Id: I561361f3fd2c3f6b7ca524614b7d7af461cc12d4
Reviewed-on: https://swiftshader-review.googlesource.com/c/SwiftShader/+/37710
Presubmit-Ready: Alexis Hétu <sugoi@google.com>
Reviewed-by: Antonio Maiorano <amaiorano@google.com>
Kokoro-Presubmit: kokoro <noreply+kokoro@google.com>
Tested-by: Alexis Hétu <sugoi@google.com>