pci: Add a function to find a device by class

There is an existing function prototype in the header file but it is not
implemented. Implement something similar.

Signed-off-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Bin Meng <bmeng.cn@gmail.com>
diff --git a/include/pci.h b/include/pci.h
index 4fbb8f6..004a048 100644
--- a/include/pci.h
+++ b/include/pci.h
@@ -644,8 +644,7 @@
 
 extern pci_dev_t pci_find_device (unsigned int vendor, unsigned int device, int index);
 extern pci_dev_t pci_find_devices (struct pci_device_id *ids, int index);
-extern pci_dev_t pci_find_class(int wanted_class, int wanted_sub_code,
-				int wanted_prog_if, int index);
+pci_dev_t pci_find_class(unsigned int find_class, int index);
 
 extern int pci_hose_config_device(struct pci_controller *hose,
 				  pci_dev_t dev,