staging: vt6655: Add spaces around arithmetic operators

This addresses the checkpatch.pl warning "spaces preferred around that
'+/-/*'"

Signed-off-by: Sebastian Fuentes <sefu1789@gmail.com>
Link: https://lore.kernel.org/r/20200912052357.GA4707@ubuntu


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>