net: devlink: don't ignore errors during dumpit

Currently, some dumpit function may end-up with error which is not
-EMSGSIZE and this error is silently ignored. Use does not have clue
that something wrong happened. Instead of silent ignore, propagate
the error to user.

Suggested-by: Andrew Lunn <andrew@lunn.ch>
Signed-off-by: Jiri Pirko <jiri@mellanox.com>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Acked-by: Jakub Kicinski <jakub.kicinski@netronome.com>
Signed-off-by: David S. Miller <davem@davemloft.net>