qed*: Conditions for changing link

There's some inconsistency in current logic determining whether the
link settings of a given interface can be changed; I.e., in all modes
other than the so-called `deault' mode the interfaces are forbidden from
changing the configuration - but even this rule is not applied to all
user APIs that may change the configuration.

Instead, let the core-module [qed] decide whether an interface can change
the configuration by supporting a new API function. We also revise the
current rule, allowing all interfaces to change their configurations while
laying the infrastructure for future modes where an interface would be
blocked from making such a configuration.

Signed-off-by: Yuval Mintz <Yuval.Mintz@qlogic.com>
Signed-off-by: David S. Miller <davem@davemloft.net>