staging: rtl8192u: remove code inside #ifdef RTL8190P in r8190_rtl8256.h

This patch removes the unused code inside #ifdef RTL8190P header guard,
since RTL8190P is not defined.

Signed-off-by: Xenia Ragiadakou <burzalodowa@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>