staging: unisys: clean up extra parens in vbuschannel_devinfo_to_string

Get rid of the unnecessary parenthesis in several assignments in
vbuschannel_devinfo_to_string().

Signed-off-by: Benjamin Romer <benjamin.romer@unisys.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>