device: Add a disabling PCIe device bus master function

A function pci_dev_disable_bus_master() is created. This function
can be used to disable Thunderbolt PCIe root ports, bridges and
devices for Vt-d based security platform at end of boot service.

BUG=None
TEST=Verified PCIe device bus master enable bit is cleared.

Signed-off-by: John Zhao <john.zhao@intel.com>
Change-Id: Ie92a15bf2c66fdc311098acb81019d4fb7f68313
Reviewed-on: https://review.coreboot.org/c/coreboot/+/41042
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Tim Wawrzynczak <twawrzynczak@chromium.org>

src/device/pci_device.c

@@ -1643,4 +1643,9 @@ void pci_assign_irqs(struct device *dev, const unsigned char pIntAtoD[4])
 #endif
 	}
 }
+
+void pci_dev_disable_bus_master(const struct device *dev)
+{
+	pci_update_config16(dev, PCI_COMMAND, ~PCI_COMMAND_MASTER, 0x0);
+}
 #endif

src/include/device/pci.h

@@ -127,6 +127,7 @@ static inline int pci_base_address_is_memory_space(unsigned int attr)
 	return (attr & PCI_BASE_ADDRESS_SPACE) == PCI_BASE_ADDRESS_SPACE_MEMORY;
 }
 
+void pci_dev_disable_bus_master(const struct device *dev);
 #endif /* CONFIG_PCI */
 
 void pci_early_bridge_init(void);