md: cleanup mddev flag clear for takeover

Commit 6995f0b (md: takeover should clear unrelated bits) clear
unrelated bits, but it's quite fragile. To avoid error in the future,
define a macro for unsupported mddev flags for each raid type and use it
to clear unsupported mddev flags. This should be less error-prone.

Suggested-by: NeilBrown <neilb@suse.com>
Signed-off-by: Shaohua Li <shli@fb.com>

drivers/md/raid5.c

@@ -62,6 +62,8 @@
 #include "raid0.h"
 #include "bitmap.h"
 
+#define UNSUPPORTED_MDDEV_FLAGS	(1L << MD_FAILFAST_SUPPORTED)
+
 #define cpu_to_group(cpu) cpu_to_node(cpu)
 #define ANY_GROUP NUMA_NO_NODE
 
@@ -7830,7 +7832,8 @@ static void *raid5_takeover_raid1(struct mddev *mddev)
 
 	ret = setup_conf(mddev);
 	if (!IS_ERR_VALUE(ret))
-		clear_bit(MD_FAILFAST_SUPPORTED, &mddev->flags);
+		mddev_clear_unsupported_flags(mddev,
+			UNSUPPORTED_MDDEV_FLAGS);
 	return ret;
 }