drm: Fix a typo in drm_ioctl.c

This patch fix a spelling typo found in
Documentation/DocBook/gpu/API-drm-ioctl-flags.html
It is because the html file was created from comments in source,
I have to fix the source.
Signed-off-by: NMasanari Iida <standby24x7@gmail.com>
Signed-off-by: NJani Nikula <jani.nikula@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/20160629234706.31209-1-standby24x7@gmail.com

drivers/gpu/drm/drm_ioctl.c

@@ -759,7 +759,7 @@ EXPORT_SYMBOL(drm_ioctl);
  * shouldn't be used by any drivers.
  *
  * Returns:
- * True if the @nr corresponds to a DRM core ioctl numer, false otherwise.
+ * True if the @nr corresponds to a DRM core ioctl number, false otherwise.
  */
 bool drm_ioctl_flags(unsigned int nr, unsigned int *flags)
 {