net: mediatek: disable all interrupts during probe

The current code only disables those IRQs that we will later use. To
ensure that we have a predefined state, we really want to disable all IRQs.
Change the code to disable all IRQs to achieve this.

Signed-off-by: John Crispin <john@phrozen.org>
Signed-off-by: David S. Miller <davem@davemloft.net>