Staging: rtl8723bs: Do not check for NOT NULL before kfree()

Do not check for NOT NULL before calling kfree because
if the pointer is NULL, no action occurs.
Done using the following semantic patch by coccinelle.

@@
expression ptr;
@@

- if (ptr != NULL)
  kfree(ptr);

Signed-off-by: Shreeya Patel <shreeya.patel23498@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>