userns: Convert drm to use kuid and kgid and struct pid where appropriate

Blink Blink this had not been converted to use struct pid ages ago?

- On drm open capture the openers kuid and struct pid.
- On drm close release the kuid and struct pid
- When reporting the uid and pid convert the kuid and struct pid
  into values in the appropriate namespace.

Cc: dri-devel@lists.freedesktop.org
Acked-by: Dave Airlie <airlied@redhat.com>
Acked-by: Serge Hallyn <serge.hallyn@canonical.com>
Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
diff --git a/include/drm/drmP.h b/include/drm/drmP.h
index d6b67bb..9bc5c6a 100644
--- a/include/drm/drmP.h
+++ b/include/drm/drmP.h
@@ -426,8 +426,8 @@
 /** File private data */
 struct drm_file {
 	int authenticated;
-	pid_t pid;
-	uid_t uid;
+	struct pid *pid;
+	kuid_t uid;
 	drm_magic_t magic;
 	unsigned long ioctl_count;
 	struct list_head lhead;