When x was flipped, the entire row would be copied in the
reverse byte order, which was wrong for any type with pixels
larger than 1 byte. Now the full pixels are copied in the
reverse order instead of the bytes, so pixels are no longer
byte flipped.

Change-Id: Ie0e0516546a49d0f890a4abe24d44ccb3ffb2350
Reviewed-on: https://swiftshader-review.googlesource.com/7362Tested-by: Alexis Hétu <sugoi@google.com>
Reviewed-by: Nicolas Capens <capn@google.com>