Staging: rtl8192e: Fix __constant_htons to htons style warning

This fixes the following checkpatch.pl warning:
WARNING: __constant_htons should be htons

Signed-off-by: Mahati Chamarthy <mahati.chamarthy@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>