There are several error handling bugs in mscc_ocelot_init_ports().  I
went through the code, and carefully audited it and made fixes and
cleanups.

1) The ocelot_probe_port() function didn't have a mirror release function
   so it was hard to follow.  I created the ocelot_release_port()
   function.
2) In the ocelot_probe_port() function, if the register_netdev() call
   failed, then it lead to a double free_netdev(dev) bug.  Fix this by
   setting "ocelot->ports[port] = NULL" on the error path.
3) I was concerned that the "port" which comes from of_property_read_u32()
   might be out of bounds so I added a check for that.
4) In the original code if ocelot_regmap_init() failed then the driver
   tried to continue but I think that should be a fatal error.
5) If ocelot_probe_port() failed then the most recent devlink was leaked.
   The fix for mostly came Vladimir Oltean.  Get rid of "registered_ports"
   and just set a bit in "devlink_ports_registered" to say when the
   devlink port has been registered (and needs to be unregistered on
   error).  There are fewer than 32 ports so a u32 is large enough for
   this purpose.
6) The error handling if the final ocelot_port_devlink_init() failed had
   two problems.  The "while (port-- >= 0)" loop should have been
   "--port" pre-op instead of a post-op to avoid a buffer underflow.
   The "if (!registered_ports[port])" condition was reversed leading to
   resource leaks and double frees.

Fixes: 6c30384e ("net: mscc: ocelot: register devlink ports")
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Reviewed-by: Vladimir Oltean <vladimir.oltean@nxp.com>
Tested-by: Vladimir Oltean <vladimir.oltean@nxp.com>
Link: https://lore.kernel.org/r/YBkXhqRxHtRGzSnJ@mwandaSigned-off-by: Jakub Kicinski <kuba@kernel.org>