ksmbd: add request buffer validation in smb2_set_info

Add buffer validation in smb2_set_info, and remove unused variable
in set_file_basic_info. and smb2_set_info infolevel functions take
structure pointer argument.

Cc: Tom Talpey <tom@talpey.com>
Cc: Ronnie Sahlberg <ronniesahlberg@gmail.com>
Cc: Ralph Böhme <slow@samba.org>
Cc: Sergey Senozhatsky <senozhatsky@chromium.org>
Acked-by: Hyunchul Lee <hyc.lee@gmail.com>
Reviewed-by: Ralph Boehme <slow@samba.org>
Signed-off-by: Namjae Jeon <linkinjeon@kernel.org>
Signed-off-by: Steve French <stfrench@microsoft.com>