smb3: fix snapshot mount option

The conversion to the new API broke the snapshot mount option
due to 32 vs. 64 bit type mismatch

Fixes: 24e0a1ef ("cifs: switch to new mount api")
Cc: stable@vger.kernel.org # 5.11+
Reported-by:  <ruckajan10@gmail.com>
Acked-by: Ronnie Sahlberg <lsahlber@redhat.com>
Signed-off-by: Steve French <stfrench@microsoft.com>