btrfs: make array types static const, reduces object code size

Don't populate the read-only array types on the stack, instead make
it static const.  Makes the object code smaller by nearly 60 bytes:

Before:
   text	   data	    bss	    dec	    hex	filename
  90536	   6552	     64	  97152	  17b80	fs/btrfs/ioctl.o

After:
   text	   data	    bss	    dec	    hex	filename
  90414	   6616	     64	  97094	  17b46	fs/btrfs/ioctl.o
Signed-off-by: NColin Ian King <colin.king@canonical.com>
Reviewed-by: NDavid Sterba <dsterba@suse.com>
Signed-off-by: NDavid Sterba <dsterba@suse.com>

fs/btrfs/ioctl.c

@@ -4114,10 +4114,12 @@ static long btrfs_ioctl_space_info(struct btrfs_fs_info *fs_info,
 	struct btrfs_ioctl_space_info *dest_orig;
 	struct btrfs_ioctl_space_info __user *user_dest;
 	struct btrfs_space_info *info;
-	u64 types[] = {BTRFS_BLOCK_GROUP_DATA,
-		       BTRFS_BLOCK_GROUP_SYSTEM,
-		       BTRFS_BLOCK_GROUP_METADATA,
-		       BTRFS_BLOCK_GROUP_DATA | BTRFS_BLOCK_GROUP_METADATA};
+	static const u64 types[] = {
+		BTRFS_BLOCK_GROUP_DATA,
+		BTRFS_BLOCK_GROUP_SYSTEM,
+		BTRFS_BLOCK_GROUP_METADATA,
+		BTRFS_BLOCK_GROUP_DATA | BTRFS_BLOCK_GROUP_METADATA
+	};
 	int num_types = 4;
 	int alloc_size;
 	int ret = 0;