vc4: cec: Restore cec physical address on reconnect

Currently we call cec_phys_addr_invalidate on a hotplug deassert.
That may be due to a TV power cycling, or an AVR being switched
on (and switching edid). This makes CEC unusable.

Set it back up again on the hotplug assert.

Signed-off-by: Dom Cobley <popcornmix@gmail.com>