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

This patch delete the 'alloc_tx_beacon_desc_ring' 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:883:5: warning: symbol 'alloc_tx_beacon_desc_ring' 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

@@ -903,12 +903,6 @@ void rtl8192_rtx_disable(struct net_device *dev)
 	return;
 }
 
-
-int alloc_tx_beacon_desc_ring(struct net_device *dev, int count)
-{
-	return 0;
-}
-
 inline u16 ieeerate2rtlrate(int rate)
 {
 	switch (rate) {