drm/imx: Remove unused field imx_drm_device.pipes

This has been unused since commit 44b460cfe554 ("drm: imx: remove struct
imx_drm_crtc and imx_drm_crtc_helper_funcs")

Signed-off-by: Leonard Crestez <leonard.crestez@nxp.com>
Signed-off-by: Philipp Zabel <p.zabel@pengutronix.de>

drivers/gpu/drm/imx/imx-drm-core.c

@@ -37,7 +37,6 @@
 
 struct imx_drm_device {
 	struct drm_device			*drm;
-	unsigned int				pipes;
 	struct drm_atomic_state			*state;
 };