switchtec: Add device IDs for PSX 24xG3 and PSX 48xG3

Add device IDs for PSX 24xG3 and PSX 48xG3.  These are valid devices that
were missing from the existing device ID table for the Switchtec driver.

Signed-off-by: Kelvin Cao <kelvin.cao@microsemi.com>
Signed-off-by: Logan Gunthorpe <logang@deltatee.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>