As with 888 and 1010102, 565 and 5551 need to be rounded before being written.

Bug: b/146633956
Change-Id: Ifea2e8f187a276a1f49effedc377612dbe338057
Reviewed-on: https://swiftshader-review.googlesource.com/c/SwiftShader/+/40368
Presubmit-Ready: Alexis Hétu <sugoi@google.com>
Kokoro-Presubmit: kokoro <noreply+kokoro@google.com>
Reviewed-by: Chris Forbes <chrisforbes@google.com>
Reviewed-by: Nicolas Capens <nicolascapens@google.com>
Tested-by: Alexis Hétu <sugoi@google.com>