eal: enable hotplug on multi-process

eal: enable hotplug on multi-process

We are going to introduce the solution to handle hotplug in
multi-process, it includes the below scenario:

1. Attach a device from the primary
2. Detach a device from the primary
3. Attach a device from a secondary
4. Detach a device from a secondary

In the primary-secondary process model, we assume devices are shared
by default. that means attaches or detaches a device on any process
will broadcast to all other processes through mp channel then device
information will be synchronized on all processes.

Any failure during attaching/detaching process will cause inconsistent
status between processes, so proper rollback action should be considered.

This patch covers the implementation of case 1,2.
Case 3,4 will be implemented on a separate patch.

IPC scenario for Case 1, 2:

attach a device
a) primary attach the new device if failed goto h).
b) primary send attach sync request to all secondary.
c) secondary receive request and attach the device and send a reply.
d) primary check the reply if all success goes to i).
e) primary send attach rollback sync request to all secondary.
f) secondary receive the request and detach the device and send a reply.
g) primary receive the reply and detach device as rollback action.
h) attach fail
i) attach success

detach a device
a) primary send detach sync request to all secondary
b) secondary detach the device and send reply
c) primary check the reply if all success goes to f).
d) primary send detach rollback sync request to all secondary.
e) secondary receive the request and attach back device. goto g)
f) primary detach the device if success goto g), else goto d)
g) detach fail.
h) detach success.

Signed-off-by: Qi Zhang <qi.z.zhang@intel.com>
Acked-by: Anatoly Burakov <anatoly.burakov@intel.com>