transaction: Fix incorrect use of __le16/32/64

transaction: Fix incorrect use of __le16/32/64

Use ceph_le16/32/64 instead of __le16/32/64 (which are no-op outside
of kernel code).

Note that this updates only those uses of __le16/32/64 which are
part of data structures that are serialized to disk/network
(i.e. Transaction::Op and Transaction::TransactionData).

Also note that code in this file performs combined operations on
little-endian values (in particular ++, +=, and |=) which are not
supported on the ceph_le16/32/64 class, and are therefore replaced
by more primitive operations.

Fixes (partially): https://tracker.ceph.com/issues/41605

Signed-off-by: Ulrich Weigand <ulrich.weigand@de.ibm.com>