staging: imx-drm: Fix typo in staging/imx-drm

Correct spelling typo in staging/imx-drm

Singed-off-by: Masanari Iida <standby24x7@gmail.com>
Acked-by: Sascha Hauer <s.hauer@pengutronix.de>

Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>