We were expecting R or RG internal formats, instead of L, A, or LA.

Change-Id: I6ee145341819460dda262b017db6d8105860f49a
Reviewed-on: https://swiftshader-review.googlesource.com/17508Tested-by: Nicolas Capens <nicolascapens@google.com>
Reviewed-by: Alexis Hétu <sugoi@google.com>