AMD workarounds relied on the vendor string containing "AMD" or
"ATI". Some vendor strings only contain "Radeon", which lead to
workarounds not being enabled.

Bug: angleproject:5004
Change-Id: Ie32852212afd1df1f3f691c87a5459e1b53b74b6
Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/2385932
Commit-Queue: Geoff Lang <geofflang@chromium.org>
Reviewed-by: Shahbaz Youssefi <syoussefi@chromium.org>
Reviewed-by: Geoff Lang <geofflang@chromium.org>