RDMA/rxe: Set sys_image_guid to be aligned with HW IB devices

RDMA/rxe: Set sys_image_guid to be aligned with HW IB devices

The RXE driver doesn't set sys_image_guid and user space applications see
zeros. This causes to pyverbs tests to fail with the following traceback,
because the IBTA spec requires to have valid sys_image_guid.

 Traceback (most recent call last):
   File "./tests/test_device.py", line 51, in test_query_device
     self.verify_device_attr(attr)
   File "./tests/test_device.py", line 74, in verify_device_attr
     assert attr.sys_image_guid != 0

In order to fix it, set sys_image_guid to be equal to node_guid.

Before:
 5: rxe0: ... node_guid 5054:00ff:feaa:5363 sys_image_guid
 0000:0000:0000:0000

After:
 5: rxe0: ... node_guid 5054:00ff:feaa:5363 sys_image_guid
 5054:00ff:feaa:5363

Fixes: 8700e3e7c485 ("Soft RoCE driver")
Link: https://lore.kernel.org/r/20200323112800.1444784-1-leon@kernel.org
Signed-off-by: Zhu Yanjun <yanjunz@mellanox.com>
Signed-off-by: Leon Romanovsky <leonro@mellanox.com>
Signed-off-by: Jason Gunthorpe <jgg@mellanox.com>