dlm: use __le types for options header

This patch changes to use __le types directly in the dlm option headers
structures which are casted at the right dlm message buffer positions.

Currently only midcomms.c using those headers which already was calling
endian conversions on-the-fly without using in/out functionality like
other endianness handling in dlm. Using __le types now will hopefully get
useful warnings in future if we do comparison against host byte order
values.

Signed-off-by: Alexander Aring <aahringo@redhat.com>
Signed-off-by: David Teigland <teigland@redhat.com>