OpenGLES 3.0 allows for more combinations of format/internalformat
for floating point types. These types were already supported, just
not using the combinations added here.

Bug chromium:763384

Change-Id: I146548c2920799c7ea0d5d537d556ba562708147
Reviewed-on: https://swiftshader-review.googlesource.com/12928Tested-by: Alexis Hétu <sugoi@google.com>
Reviewed-by: Nicolas Capens <nicolascapens@google.com>