staging: rtl8192u: Deleted 'rtl819xU_cmd_isr' function in r8192U_core.c

This patch delete the 'rtl819xU_cmd_isr' function that is not used in
anywhere in the driver.

Fix the following sparse warning in r8192U_core.c

drivers/staging/rtl8192u/r8192U_core.c:1516:6: warning: symbol 'rtl819xU_cmd_isr' was not declared. Should it be static?
Signed-off-by: Ana Rey <anarey@gmail.com>
Signed-off-by: Peter P Waskiewicz Jr <peter.p.waskiewicz.jr@intel.com>

drivers/staging/rtl8192u/r8192U_core.c

@@ -1555,11 +1555,6 @@ u16 N_DBPSOfRate(u16 DataRate)
 	return N_DBPS;
 }
 
-void rtl819xU_cmd_isr(struct urb *tx_cmd_urb, struct pt_regs *regs)
-{
-	usb_free_urb(tx_cmd_urb);
-}
-
 unsigned int txqueue2outpipe(struct r8192_priv *priv, unsigned int tx_queue)
 {
 	if (tx_queue >= 9) {