ARM devices cast float to unsigned int differently than Intel devices.
Need to do additional work to ensure consistent behavior.
This was causing negative API tests to fail because the invalid
parameter was being turned into a 0 which is valid, but not what was
intended (should have been 0xffffffff).

Bug: angleproject:4323
Change-Id: I7447842d0f56362d9eb2db4d04b5416c78e51d27
Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/2012746
Commit-Queue: Courtney Goeltzenleuchter <courtneygo@google.com>
Reviewed-by: Geoff Lang <geofflang@chromium.org>