rtlwifi: rtl8192cu: Add routine trx

Add routine rtlwifi/rtl8192cu/trx.c. This routine differs from the rtl8192ce
file of the same name.
Signed-off-by: NGeorge <george0505@realtek.com>
Signed-off-by: NLarry Finger <Larry.Finger@lwfinger.net>
Signed-off-by: NJohn W. Linville <linville@tuxdriver.com>