radeon: set swrast_renderbuffer::ColorType field when mapping renderbuffers

Fixes http://bugs.freedesktop.org/show_bug.cgi?id=47375

NOTE: This is a candidate for the 8.0 branch.

Tested-by: Barto <mister.freeman@laposte.net>

src/mesa/drivers/dri/radeon/radeon_span.c

@@ -66,6 +66,8 @@ radeon_renderbuffer_map(struct gl_context *ctx, struct gl_renderbuffer *rb)
 
 	rrb->base.Map = map;
 	rrb->base.RowStride = stride;
+	/* No floating point color buffers, use GLubytes */
+	rrb->Base.ColorType = GL_UNSIGNED_BYTE;
 }
 
 static void