dm: sandbox: pci: Add a PCI emulation uclass

Since sandbox does not have real devices (unless it borrows those from the
host) it must use emulations. Provide a uclass which permits PCI operations
to be passed through to an emulation device.

Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/include/dm/uclass-id.h b/include/dm/uclass-id.h
index b984407..0b6e850 100644
--- a/include/dm/uclass-id.h
+++ b/include/dm/uclass-id.h
@@ -20,6 +20,7 @@
 	UCLASS_TEST_BUS,
 	UCLASS_SPI_EMUL,	/* sandbox SPI device emulator */
 	UCLASS_I2C_EMUL,	/* sandbox I2C device emulator */
+	UCLASS_PCI_EMUL,	/* sandbox PCI device emulator */
 	UCLASS_SIMPLE_BUS,
 
 	/* U-Boot uclasses start here */