The _u prefix was missing from blocks and their fields.

Bug: angleproject:4889
Change-Id: I31f3b393bc81352c8cf7a433dd652692833fc3f7
Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/2953368
Commit-Queue: Shahbaz Youssefi <syoussefi@chromium.org>
Reviewed-by: Jamie Madill <jmadill@chromium.org>
Reviewed-by: Tim Van Patten <timvp@google.com>