mlx4_core: Reset device when internal error is detected

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>