Update to Vulkan validation layers pointed out that
vkFlushMappedMemoryRanges needs to be called when the memory is mapped.

Bug: b:151820847
Change-Id: I3860306080bca435c063046f9ae20943a8601d17
Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/2108705Reviewed-by: Cody Northrop <cnorthrop@google.com>
Reviewed-by: Ian Elliott <ianelliott@google.com>
Commit-Queue: Courtney Goeltzenleuchter <courtneygo@google.com>