Revert "brcmbca: BCM recommended to handle shutdown event to unload WLAN driver"

This reverts commit 5b3fd950.

brcmbca/base-files/etc/init.d/wifi_bringup

@@ -3,7 +3,6 @@
 # Prepare the NVRAM and load Broadcom wifi drivers
 
 START=18
-STOP=18
 
 # Function:
 # Tries to find a NVRAM file supplied by the manufacturer and use this as source.
@@ -186,9 +185,3 @@ boot() {
 
 	return 0
 }
-
-############ shutdown-function ############
-shutdown() {
-	/etc/init.d/bcm-wlan-drivers.sh stop
-	sleep 3
-}