Link to bluetooth firmware for some AP6212 devices

Some AP6212 devices need the /lib/firmware/ap6212/bcm43438a1.hcd
firmware but they search for /lib/firmware/brcm/BCM43430A1.hcd.
Add a link so that it can find the right firmware.

This is needed for bluetooth on the BananaPi M2 Zero.

brcm/BCM43430A1.hcd

+../ap6212/bcm43438a1.hcd
\ No newline at end of file