PCI: Add PCI_EXT_CAP_ID_PL_32GT define

Add the define for PCI_EXT_CAP_ID_PL_32GT for drivers that will want this
whilst doing Gen5/Gen6 accesses.

Link: https://lore.kernel.org/r/20230531095713.293229-1-ben.dooks@codethink.co.ukSigned-off-by: Ben Dooks <ben.dooks@sifive.com>
Signed-off-by: Ben Dooks <ben.dooks@codethink.co.uk>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>

include/uapi/linux/pci_regs.h

@@ -738,6 +738,7 @@
 #define PCI_EXT_CAP_ID_DVSEC	0x23	/* Designated Vendor-Specific */
 #define PCI_EXT_CAP_ID_DLF	0x25	/* Data Link Feature */
 #define PCI_EXT_CAP_ID_PL_16GT	0x26	/* Physical Layer 16.0 GT/s */
+#define PCI_EXT_CAP_ID_PL_32GT  0x2A    /* Physical Layer 32.0 GT/s */
 #define PCI_EXT_CAP_ID_DOE	0x2E	/* Data Object Exchange */
 #define PCI_EXT_CAP_ID_MAX	PCI_EXT_CAP_ID_DOE