drm/pci: Only build drm_pci.c if CONFIG_PCI is set

Non-PCI systems should not build PCI helpers. Set up source code, header
file and Makefile accordingly.

Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
Reviewed-by: Emil Velikov <emil.velikov@collabora.com>
Reviewed-by: Alex Deucher <alexander.deucher@amd.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20191203100406.9674-2-tzimmermann@suse.de
diff --git a/include/drm/drm_pci.h b/include/drm/drm_pci.h
index 8181e9e..029352f 100644
--- a/include/drm/drm_pci.h
+++ b/include/drm/drm_pci.h
@@ -38,24 +38,52 @@ struct drm_dma_handle;
 struct drm_device;
 struct drm_driver;
 struct drm_master;
+struct pci_device;
+
+#ifdef CONFIG_PCI
 
 struct drm_dma_handle *drm_pci_alloc(struct drm_device *dev, size_t size,
 				     size_t align);
 void drm_pci_free(struct drm_device *dev, struct drm_dma_handle * dmah);
 
-int drm_legacy_pci_init(struct drm_driver *driver, struct pci_driver *pdriver);
-void drm_legacy_pci_exit(struct drm_driver *driver, struct pci_driver *pdriver);
-#ifdef CONFIG_PCI
 int drm_get_pci_dev(struct pci_dev *pdev,
 		    const struct pci_device_id *ent,
 		    struct drm_driver *driver);
+
+int drm_legacy_pci_init(struct drm_driver *driver, struct pci_driver *pdriver);
+void drm_legacy_pci_exit(struct drm_driver *driver, struct pci_driver *pdriver);
+
 #else
+
+static inline struct drm_dma_handle *drm_pci_alloc(struct drm_device *dev,
+						   size_t size, size_t align)
+{
+	return NULL;
+}
+
+static inline void drm_pci_free(struct drm_device *dev,
+				struct drm_dma_handle *dmah)
+{
+}
+
 static inline int drm_get_pci_dev(struct pci_dev *pdev,
 				  const struct pci_device_id *ent,
 				  struct drm_driver *driver)
 {
 	return -ENOSYS;
 }
+
+static inline int drm_legacy_pci_init(struct drm_driver *driver,
+				      struct pci_driver *pdriver)
+{
+	return -EINVAL;
+}
+
+static inline void drm_legacy_pci_exit(struct drm_driver *driver,
+				       struct pci_driver *pdriver)
+{
+}
+
 #endif
 
 #endif /* _DRM_PCI_H_ */