rtlwifi: rtl8192cu: Add new firmware

Vendor driver rtl8188C_8192C_8192D_usb_linux_v3.4.2_3727.20120404 introduced
new firmware for these chips. The code try for the new file, and fall back to
the original firmware if the new file is not available.

Signed-off-by: Larry Finger <Larry.Finger@lwfinger.net>
Cc: Stable <stable@vger.kernel.org>
Signed-off-by: John W. Linville <linville@tuxdriver.com>