ksmbd: Fix memory leak in get_file_all_info()

ksmbd: Fix memory leak in get_file_all_info()

In get_file_all_info(), if vfs_getattr() fails, the function returns
immediately without freeing the allocated filename, leading to a memory
leak.

Fix this by freeing the filename before returning in this error case.

Fixes: 5614c8c487f6a ("ksmbd: replace generic_fillattr with vfs_getattr")
Signed-off-by: Zilin Guan <zilin@seu.edu.cn>
Acked-by: Namjae Jeon <linkinjeon@kernel.org>
Signed-off-by: Steve French <stfrench@microsoft.com>