brcm80211: fmac: fix a couple checking after dereference bugs

There were two dereferencing before checking for NULL static checker
complaints in this new file.  The list cursor is never NULL so that
check can be removed.  I moved the other dereference after the check.

Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Acked-by: Arend van Spriel <arend@broadcom.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>