Reset the device when an internal error is detected.

Also, detect errors by polling the error buffer rather than using
interrupts.  This is more robust and doesn't depend on MSI-X.  Remove
the old interrupt handler entirely, since we don't want to support two
mechanisms for detecting internal errors.
Signed-off-by: Jack Morgenstein <jackm@dev.mellanox.co.il>
Signed-off-by: Roland Dreier <rolandd@cisco.com>