PCI: aardvark: Add support for PCI Bridge Subsystem Vendor ID on emulated bridge

Register with Subsystem Device/Vendor ID is at offset 0x2c.

Export it via the emulated bridge to enable support for the Subsystem
Device/Vendor ID - by reading it in the PCI controller config space and
storing it in the emulated bridge control structures, so that it is
exposed in the respective PCI capability.

After this change Subsystem ID is visible in lspci output at line:

  Capabilities: [40] Subsystem

Link: https://lore.kernel.org/r/20220711225915.13896-1-pali@kernel.orgSigned-off-by: Pali Rohár <pali@kernel.org>
Signed-off-by: Lorenzo Pieralisi <lpieralisi@kernel.org>

drivers/pci/controller/pci-aardvark.c

@@ -33,6 +33,7 @@
 #define PCIE_CORE_DEV_ID_REG					0x0
 #define PCIE_CORE_CMD_STATUS_REG				0x4
 #define PCIE_CORE_DEV_REV_REG					0x8
+#define PCIE_CORE_SSDEV_ID_REG					0x2c
 #define PCIE_CORE_PCIEXP_CAP					0xc0
 #define PCIE_CORE_PCIERR_CAP					0x100
 #define PCIE_CORE_ERR_CAPCTL_REG				0x118
@@ -1077,6 +1078,8 @@ static int advk_sw_pci_bridge_init(struct advk_pcie *pcie)
 	/* Indicates supports for Completion Retry Status */
 	bridge->pcie_conf.rootcap = cpu_to_le16(PCI_EXP_RTCAP_CRSVIS);
 
+	bridge->subsystem_vendor_id = advk_readl(pcie, PCIE_CORE_SSDEV_ID_REG) & 0xffff;
+	bridge->subsystem_id = advk_readl(pcie, PCIE_CORE_SSDEV_ID_REG) >> 16;
 	bridge->has_pcie = true;
 	bridge->data = pcie;
 	bridge->ops = &advk_pci_bridge_emul_ops;