net: qcom/emac: add an error interrupt handler for the sgmii

The SGMII (internal PHY) can report decode errors via an interrupt.  It
can also report autonegotiation status changes, but we don't need to track
those.  The SGMII can recover automatically from most decode errors, so
we only reset the interface if we get multiple consecutive errors.

It's possible for bogus decode errors to be reported while the link is
being brought up.  The interrupt is registered when the interface is
opened, and it's enabled after the link is up.

Signed-off-by: Timur Tabi <timur@codeaurora.org>
Signed-off-by: David S. Miller <davem@davemloft.net>