staging: rtl8712: rtl871x_ioctl_set: Remove unused macro

Removed Unused macro IS_MAC_ADDRESS_BROADCAST.
Grep'd to find occurences.

Signed-off-by: Bhaktipriya Shridhar <bhaktipriya96@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>