include: Fix new-style encoding routines on big-endian

include: Fix new-style encoding routines on big-endian

The new-style encoding routines (denc.h) are broken on big-endian
systems.  While there is a lot of infrastucture in place to
recognize data types that need to be byte-swapped during encoding
and decoding on big-endian systems, nothing is actually ever swapped.

Fixed by using ceph_le16/32/64 instead of __le16/32/64 (which are
no-ops outside of kernel code).

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

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