ksmbd: allow write with FILE_APPEND_DATA

Windows client write with FILE_APPEND_DATA when using git.
ksmbd should allow write it with this flags.

Z:\test>git commit -m "test"
fatal: cannot update the ref 'HEAD': unable to append to
 '.git/logs/HEAD': Bad file descriptor

Fixes: 0626e664 ("cifsd: add server handler for central processing and tranport layers")
Cc: stable@vger.kernel.org # v5.15+
Signed-off-by: Namjae Jeon <linkinjeon@kernel.org>
Signed-off-by: Steve French <stfrench@microsoft.com>