Make 1-bit fields be unsigned (no sign bit :).

sparse complains about them:
drivers/char/drm/sis_ds.h:88:12: warning: dubious one-bit signed bitfield
drivers/char/drm/sis_ds.h:89:16: warning: dubious one-bit signed bitfield
Signed-off-by: Randy Dunlap <rddunlap@osdl.org>
Signed-off-by: Dave Airlie <airlied@linux.ie>

drivers/char/drm/sis_ds.h

@@ -85,8 +85,8 @@ struct mem_block_t {
 	struct mem_block_t *heap;
 	int ofs,size;
 	int align;
-	int free:1;
-	int reserved:1;
+	unsigned int free:1;
+	unsigned int reserved:1;
 };
 typedef struct mem_block_t TMemBlock;
 typedef struct mem_block_t *PMemBlock;