staging: rtl8192u: do not use undefined $(TOPDIR) in Makefile

drivers/staging/rtl8192u/ieee80211/Makefile uses $(TOPDIR) to configure
an include directory, without defining this variable first. The path
which is configured is therefore "/drivers/net/wireless", which does not
seem to be the intended path.

Remove the offending line.
Signed-off-by: Nicolas Iooss <nicolas.iooss_linux@m4x.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/rtl8192u/ieee80211/Makefile

 NIC_SELECT = RTL8192U
 
-ccflags-y := -I$(TOPDIR)/drivers/net/wireless
-ccflags-y += -O2
+ccflags-y := -O2
 ccflags-y += -DJACKSON_NEW_8187 -DJACKSON_NEW_RX
 
 ieee80211-rsl-objs := ieee80211_rx.o \