staging: rtl8187se: Added parenthesis in a macro in r8180.h

This patch adds parentheses to enclose a complex value in a macro as a the
CodingStyle recommends.

This errors was found by checkpatch.pl script

Signed-off-by: Ana Rey <anarey@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>