staging: emxx_udc: Replace __constant_cpu_to_le16 with cpu_to_le16

This fixes the following checkpatch.pl warning:
WARNING: __constant_cpu_to_le16 should be cpu_to_le16
Additionally, it removes the space between function name and (.

Signed-off-by: Roberta Dobrescu <roberta.dobrescu@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>