smb: common: change the data type of num_aces to le16

2.4.5 in [MS-DTYP].pdf describe the data type of num_aces as le16.

AceCount (2 bytes): An unsigned 16-bit integer that specifies the count
of the number of ACE records in the ACL.

Change it to le16 and add reserved field to smb_acl struct.

Reported-by: Igor Leite Ladessa <igor-ladessa@hotmail.com>
Tested-by: Igor Leite Ladessa <igor-ladessa@hotmail.com>
Signed-off-by: Namjae Jeon <linkinjeon@kernel.org>
Signed-off-by: Steve French <stfrench@microsoft.com>