cifsd: Fix regression in smb2_get_info

a Windows 10 client isn't able to store files from ksmbd servers due
unknown local permission problems (code 0x8007003A) if smb3 encryption
is enabled. Windows 10 is requesting for ATTRIBUTE_SECINFO (mask 0x20)
which is not yet handled by ksmbd, this leads to a invalid response.
For now we just reintroduce the old check to avoid processing of unhandled
flags until ATTRIBUTE_SECINFO is properly handled.

Signed-off-by: Sebastian Gottschall <s.gottschall@dd-wrt.com>
Signed-off-by: Namjae Jeon <namjae.jeon@samsung.com>
Signed-off-by: Steve French <stfrench@microsoft.com>