etsec: fix IRQ (un)masking

etsec: fix IRQ (un)masking

Interrupt conditions occurring while masked are not being
signaled when later unmasked.
The fix is to raise/lower IRQs when IMASK is changed.

To avoid problems like this in future, consolidate
IRQ pin update logic in one function.

Also fix probable typo "IEVENT_TXF | IEVENT_TXF",
and update IRQ pins on reset.

Signed-off-by: Michael Davidsaver <mdavidsaver@gmail.com>
Reviewed-by: Cédric Le Goater <clg@kaod.org>
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>