radeon: Remove dead STANDALONE_MMIO defines

These were, at some point in the past, used to request that Xorg's
compiler.h export a static inline xf86ReadMmio32 instead of a function
pointer. compiler.h only has this option for DEC Alpha.

But Xorg's compiler.h isn't being included by either of these two files
and the radeon driver still works on Alpha, so the definitions are dead
and not needed.

Reviewed-by: Michel Dänzer <michel.daenzer@amd.com>

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

@@ -49,8 +49,6 @@ WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
 #include "radeon_common.h"
 #include "radeon_ioctl.h"
 
-#define STANDALONE_MMIO
-
 #define RADEON_TIMEOUT             512
 #define RADEON_IDLE_RETRY           16
 

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

@@ -44,7 +44,6 @@ WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
 #include "main/fbobject.h"
 #include "swrast/s_renderbuffer.h"
 
-#define STANDALONE_MMIO
 #include "radeon_chipset.h"
 #include "radeon_macros.h"
 #include "radeon_screen.h"