e1000: Don't run e1000_instance_init() twice

e1000: Don't run e1000_instance_init() twice

QOM object initialization runs .instance_init() for the type and all
its supertypes; see object_init_with_type().

Both TYPE_E1000_BASE and its concrete subtypes set .instance_init() to
e1000_instance_init().  For the concrete subtypes, it duly gets run
twice.  The second run fails, but the error gets ignored (a later
commit will change that).

Remove it from the subtypes.

Cc: Jason Wang <[email protected]>
Signed-off-by: Markus Armbruster <[email protected]>
Acked-by: Jason Wang <[email protected]>
Reviewed-by: Paolo Bonzini <[email protected]>
Message-Id: <20200505152926[email protected]>