On Radeon GPUs VK_IMAGE_LAYOUT_GENERAL images don't use Delta Color
Compression, but SRC/DST optimal images do. Transitioning from GENERAL
to SRC/DST causes a big performance hit.

As a next step we should try harder to avoid VK_IMAGE_LAYOUT_GENERAL.
Signed-off-by: Stefan Dösinger <stefan@codeweavers.com>