IB/core: IB/core: Allow legacy verbs through extended interfaces

When an extended verb is an extension to a legacy verb, the original
functionality is preserved. Hence we do not require each hardware driver
to set the extended capability. This will allow the use of the extended
verb in its simple form with drivers that do not support the extended
capability.

Signed-off-by: Eli Cohen <eli@mellanox.com>
Signed-off-by: Leon Romanovsky <leonro@mellanox.com>
Signed-off-by: Doug Ledford <dledford@redhat.com>