staging: rtl8187se: add missing __iomem annotation

Fix the following type of sparse warnings:

drivers/staging/rtl8187se/r8180_core.c:163:48: warning: incorrect type in argument 1 (different address spaces)
drivers/staging/rtl8187se/r8180_core.c:163:48:    expected void const volatile [noderef] <asn:2>*addr
drivers/staging/rtl8187se/r8180_core.c:163:48:    got unsigned char [usertype] *

Signed-off-by: Teodora Baluta <teobaluta@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>