staging:rtl8187se: Fix sparse warning in right shift

This patch fixes the following sparse warning:
drivers/staging/rtl8187se/r8180_core.c:1328:40: warning: right shift by bigger than source value
by adding parenthesis.

Signed-off-by: Himangi Saraogi <himangi774@gmail.com>
Acked-by: Bob Copeland <me@bobcopeland.com>
Signed-off-by: Peter P Waskiewicz Jr <peter.p.waskiewicz.jr@intel.com>