ksmbd: fix uninitialized pointer read in smb2_create_link()

There is a case that file_present is true and path is uninitialized.
This patch change file_present is set to false by default and set to
true when patch is initialized.

Fixes: 74d7970f

 ("ksmbd: fix racy issue from using ->d_parent and ->d_name")
Reported-by: Coverity Scan <scan-admin@coverity.com>
Signed-off-by: Namjae Jeon <linkinjeon@kernel.org>
Signed-off-by: Steve French <stfrench@microsoft.com>