rtlwifi: Fix build when RTL8192CU is selected, but RTL8192CE is not

The wireless Makefile does not build rtlwifi for rtl8192cu unless
rtl8192ce is selected.

Signed-off-by: Willy Tarreau <w@1wt.eu>
Signed-off-by: Larry Finger <Larry.Finger@lwfinger.net>
Signed-off-by: John W. Linville <linville@tuxdriver.com>