btrfs-progs: Add missing exit for parse_profile function

In parse_profile() function, in error handling route, it output error
message but forgot to exit(1), causing even profile is not valid, it
will just fallback to single.

Reported-by: James Harvey <jamespharvey20@gmail.com>
Signed-off-by: Qu Wenruo <quwenruo@cn.fujitsu.com>
Signed-off-by: David Sterba <dsterba@suse.com>

mkfs.c

@@ -356,6 +356,7 @@ static u64 parse_profile(char *s)
 		return 0;
 	} else {
 		fprintf(stderr, "Unknown profile %s\n", s);
+		exit(1);
 	}
 	/* not reached */
 	return 0;