staging: imx-drm: Fix build error

Instead of redefining the enums, use the standard ones already
available to avoid the following build errors:

drivers/staging/imx-drm/imx-hdmi.c:56:13: error: nested redefinition of ‘enum hdmi_colorimetry’
drivers/staging/imx-drm/imx-hdmi.c:56:13: error: redeclaration of ‘enum hdmi_colorimetry’
In file included from include/drm/drm_crtc.h:33:0,
                 from include/drm/drmP.h:710,
                 from drivers/staging/imx-drm/imx-hdmi.c:24:
include/linux/hdmi.h:48:6: note: originally defined here

Reported-by: Josh Boyer <jwboyer@fedoraproject.org>
Signed-off-by: Sachin Kamat <sachin.kamat@linaro.org>
Cc: Guennadi Liakhovetski <g.liakhovetski@gmx.de>
Reviewed-by: Fabio Estevam <fabio.estevam@freescale.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>