PCI/switchtec: Rename generation-specific constants

Gen4 hardware will have different values for the SWITCHTEC_X_RUNNING and
SWITCHTEC_IOCTL_NUM_PARTITIONS, so rename them with GEN3 in their name.

No functional changes intended.

Link: https://lore.kernel.org/r/20200115035648.2578-2-logang@deltatee.com


Signed-off-by: Logan Gunthorpe <logang@deltatee.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>