MFC r352991 and 353000:

MFC r352991 and 353000:
Wait for FW readiness before initializing command interface in mlx5core.

Before attempting to initialize the command interface we must wait till
the fw_initializing bit is clear.

If we fail to meet this condition the hardware will drop our
configuration, specifically the descriptors page address.  This scenario
can happen when the firmware is still executing an FLR flow and did not
finish yet so the driver needs to wait for that to finish.

Linux commits:
6c780a0267b8
b8a92577f4be.

Sponsored by:	Mellanox Technologies