Enable and fix hardware buffer management. Also fix the IRQ storm caused by a
misconfiguration of the PCA9538 interrupt pin.

Reviewed-by: Tomasz Maciej Nowak <tmn505@gmail.com>
Tested-by: Tomasz Maciej Nowak <tmn505@gmail.com>
Signed-off-by: Rui Salvaterra <rsalvaterra@gmail.com>