freedreno/a6xx: Move blit check so as to restore comment

freedreno/a6xx: Move blit check so as to restore comment

The explanation for the compressed format check is broken across two
comments:

	/* We can blit if both or neither formats are compressed formats... */
	/* ... but only if they're the same compression format. */

but the ok_format() checks were inserted between, breaking up the flow
of the sentence.

Reviewed-by: Rob Clark <robdclark@gmail.com>
Signed-off-by: Kristian H. Kristensen <hoegsberg@chromium.org>