staging: rtl8192u: remove unused Makefile

drivers/staging/rtl8192u/ieee80211/Makefile is not used at all.
All the build rules are described in drivers/staging/rtl8192u/Makefile.
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Link: https://lore.kernel.org/r/20200104162136.19170-1-masahiroy@kernel.orgSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/rtl8192u/ieee80211/Makefile

-# SPDX-License-Identifier: GPL-2.0
-NIC_SELECT = RTL8192U
-
-ccflags-y := -O2
-ccflags-y += -DJACKSON_NEW_8187 -DJACKSON_NEW_RX
-
-ieee80211-rsl-objs := ieee80211_rx.o \
-		      ieee80211_softmac.o \
-		      ieee80211_tx.o \
-		      ieee80211_wx.o \
-		      ieee80211_module.o \
-		      ieee80211_softmac_wx.o\
-		      rtl819x_HTProc.o\
-		      rtl819x_TSProc.o\
-		      rtl819x_BAProc.o\
-		      dot11d.o
-
-ieee80211_crypt-rsl-objs := ieee80211_crypt.o
-ieee80211_crypt_tkip-rsl-objs := ieee80211_crypt_tkip.o
-ieee80211_crypt_ccmp-rsl-objs := ieee80211_crypt_ccmp.o
-ieee80211_crypt_wep-rsl-objs := ieee80211_crypt_wep.o
-
-obj-m +=ieee80211-rsl.o
-obj-m +=ieee80211_crypt-rsl.o
-obj-m +=ieee80211_crypt_wep-rsl.o
-obj-m +=ieee80211_crypt_tkip-rsl.o
-obj-m +=ieee80211_crypt_ccmp-rsl.o