staging: rtl8192u: remove unused code in fw_download_code()

This patch removes the code that resides outside #ifdef RTL8192U,
since RTL8192U is defined in r8192U.h and removes, also, the header
guard itself.

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