rtl8180: remove too-early-added rtl8187se enum value

While changing board-type variable to enum, I have added enum
value for rtl8187se by mistake.
This will causes gcc warnings with unhandled switch/cases.

Remove it temporarily until I will push also rtl8187se changes.

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