ksmbd: initialize FileSystemControlFlags in FS_CONTROL_INFORMATION

In the Linux kernel, the following vulnerability has been resolved:

ksmbd: initialize FileSystemControlFlags in FS_CONTROL_INFORMATION

smb2_get_info_filesystem() reports 48 bytes for FS_CONTROL_INFORMATION,
that is the whole of struct smb2_fs_control_info, but never assigns
FileSystemControlFlags. Those four bytes go to the client as they are
found in the response buffer.

The buffer is zeroed on allocation, so a standalone request leaks
nothing. A compound request can leak: the offset of the next response
is advanced by the length pinned for the previous one, so a reply that
was written into the buffer and then dropped in favour of the short
error response of smb2_set_err_rsp() stays there, and the next reply is
laid over it with only the header cleared.

ksmbd does not implement quota tracking, so report no control flags.