OpenGL ES does not support conversion from the given data format
to the internal format with glTexImage2D.

Use the given data format as the internal format, and ignore
the given alpha channels with GL_TEXTURE_SWIZZLE_A in case the
format contains alpha channels.

Signed-off-by: Akihiko Odaki <akihiko.odaki@gmail.com>
Message-Id: <20210219094803.90860-1-akihiko.odaki@gmail.com>
Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>