rtl8180: add ERP configuration for rtl8187se

This patch adds ERP configuration support for rtl8187se to the
existing ERP configuration function.
It needs a different register offset and it must not apply
rtl8185 workaround.

Signed-off-by: Andrea Merello <andrea.merello@gmail.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>