drm/radeon: fix endian bugs in hw i2c atom routines

commit 4543eda52113d1e2cc0e9bf416f79597e6ef1ec7 upstream.

Need to swap the data fetched over i2c properly.  This
is the same fix as the endian fix for aux channel
transactions.

Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>