zonefs: Prevent uninitialized symbol 'size' warning

In zonefs_file_dio_append(), initialize the variable size to 0 to
prevent compilation and static code analizers warning such as:

New smatch warnings:
fs/zonefs/file.c:441 zonefs_file_dio_append() error: uninitialized
symbol 'size'.

The warning is a false positive as size is never actually used
uninitialized.

No functional change.

Reported-by: kernel test robot <[email protected]>
Reported-by: Dan Carpenter <[email protected]>
Link: https://lore.kernel.org/r/[email protected]/
Signed-off-by: Damien Le Moal <[email protected]>
Reviewed-by: Johannes Thumshirn <[email protected]>
Reviewed-by: Himanshu Madhani <[email protected]>

Author: Damien Le Moal

fs/zonefs/file.c

@@ -383,7 +383,7 @@ static ssize_t zonefs_file_dio_append(struct kiocb *iocb, struct iov_iter *from)
 	struct block_device *bdev = inode->i_sb->s_bdev;
 	unsigned int max = bdev_max_zone_append_sectors(bdev);
 	struct bio *bio;
-	ssize_t size;
+	ssize_t size = 0;
 	int nr_pages;
 	ssize_t ret;