staging: rtl8723bs: Remove unnecessary initializations

Remove initializations of global variables with 0.
Criticized by checkpatch.

Signed-off-by: Henriette Hofmeier <passt@h-hofmeier.de>
Signed-off-by: Florian Harbecke <florian.harbecke@fau.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>