rtlwifi: Fix build warning introduced by commit a2905935

The kbuild test robot reports the following warning with x86_64-randconfig-x955:

warning: (RTL8192CE && RTL8192SE && RTL8192DE && RTL8723AE && RTL8192CU) selects
 RTLWIFI which has unmet direct dependencies (NETDEVICES && WLAN &&
 (RTL8192CE || RTL8192CU || RTL8192SE || RTL8192DE))

This warning was introduced in commit a2905935, "rtlwifi: Modify files for addition
of rtl8723ae", and is d ue to a missing dependence of RTLWIFI on RTL8723AE.

Signed-off-by: Larry Finger <Larry.Finger@lwfinger.net>
Cc: kbuild test robot <fengguang.wu@intel.com>
Reported-by: kbuild test robot <fengguang.wu@intel.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>