Vulkan: Simplify active uniform check Bug: angleproject:7220 Change-Id: Ic0f26f3d09bac570d4ed3f791c456d569208424a Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/4636869 Reviewed-by: Charlie Lao <cclao@google.com> Commit-Queue: Shahbaz Youssefi <syoussefi@chromium.org>