drm: Replace filp in ioctl arguments with drm_file *file_priv.

As a fallout, replace filp storage with file_priv storage for "unique
identifier of a client" all over the DRM.  There is a 1:1 mapping, so this
should be a noop.  This could be a minor performance improvement, as everyth
on Linux dereferenced filp to get file_priv anyway, while only the mmap ioct
went the other direction.

Signed-off-by: Dave Airlie <airlied@linux.ie>
diff --git a/drivers/char/drm/drm_ioc32.c b/drivers/char/drm/drm_ioc32.c
index 462f46f..2286f33 100644
--- a/drivers/char/drm/drm_ioc32.c
+++ b/drivers/char/drm/drm_ioc32.c
@@ -1040,7 +1040,7 @@
  * Called whenever a 32-bit process running under a 64-bit kernel
  * performs an ioctl on /dev/drm.
  *
- * \param filp file pointer.
+ * \param file_priv DRM file private.
  * \param cmd command.
  * \param arg user argument.
  * \return zero on success or negative number on failure.