scsi: mpi3mr: Fix device loss during enclosure reboot due to zero link speed

scsi: mpi3mr: Fix device loss during enclosure reboot due to zero link speed

During enclosure reboot or expander reset, firmware may report a link
speed of 0 in "Device Add" events while the link is still coming up.
The driver drops such devices, leaving them missing even after the link
recovers.

Fix this by treating link speed 0 as 1.5 Gbps during device addition so
the device is exposed to the OS. The actual link speed will be updated
later when link-up events arrive.

Signed-off-by: Chandrakanth Patil <chandrakanth.patil@broadcom.com>
Link: https://lore.kernel.org/r/20250820084138.228471-2-chandrakanth.patil@broadcom.com
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>