crypto/scheduler: add fail-over scheduling mode

crypto/scheduler: add fail-over scheduling mode

Fail-over mode works with 2 slaves, primary slave and secondary slave.
In this mode, the scheduler will enqueue the incoming crypto op burst
to the primary slave. When one or more crypto ops are failed to be
enqueued, they then will be enqueued to the secondary slave.

Signed-off-by: Fan Zhang <roy.fan.zhang@intel.com>
Acked-by: Declan Doherty <declan.doherty@intel.com>