staging: rtl8723bs: remove null check before kfree

Kfree on NULL pointer is a no-op and therefore checking is redundant.

Signed-off-by: Himanshu Jha <himanshujha199640@gmail.com>
Acked-by: Larry Finger <Larry.Finger@lwfinger.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>