avcodec/roqvideoenc: More verbose warning about no power of 2 dimensions

Thanks-to: Vitor Sessak <vitor1001@gmail.com>
Signed-off-by: Michael Niedermayer <michaelni@gmx.at>
avcodec/roqvideoenc: Print the correct max resolution

Thanks-to: Vitor Sessak <vitor1001@gmail.com>
Signed-off-by: Michael Niedermayer <michaelni@gmx.at>