f2fs: optimize f2fs_write_cache_pages

The if statement "goto continue_unlock" is exactly the same when
each if condition is true that is depended on the value of both
"step" and "is_cold_data(page)" are 0 or 1. That means when the
value of "step" equals to "is_cold_data(page)", the if condition
is true and the if statement "goto continue_unlock" appears only
once, so it can be optimized to reduce the duplicated code.
Signed-off-by: NTiezhu Yang <kernelpatch@126.com>
Signed-off-by: NJaegeuk Kim <jaegeuk@kernel.org>

fs/f2fs/data.c

@@ -1207,9 +1207,7 @@ static int f2fs_write_cache_pages(struct address_space *mapping,
 				goto continue_unlock;
 			}
 
-			if (step == 0 && !is_cold_data(page))
-				goto continue_unlock;
-			if (step == 1 && is_cold_data(page))
+			if (step == is_cold_data(page))
 				goto continue_unlock;
 
 			if (PageWriteback(page)) {