staging: hp100: Add space around operator +

Add space around operator + to improve code readability.
Reported by checkpatch.pl

Signed-off-by: Soumyajit Deb <debsoumyajit100@gmail.com>
Link: https://lore.kernel.org/r/20200323054836.48816-2-debsoumyajit100@gmail.com


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