drm/exynos: use a new anon file for exynos gem mmaper

This patch resolves potential deadlock issue that can be incurred
by changing file->f_op and filp->private_data to exynos specific
mapper ops and gem object temporarily.

To resolve this issue, this patch creates a new anon file dedicated
to exynos specific mmaper, and making it used instead of existing one.

Signed-off-by: Inki Dae <inki.dae@samsung.com>
Signed-off-by: Kyungmin Park <kyungmin.park@samsung.com>
diff --git a/drivers/gpu/drm/exynos/exynos_drm_drv.h b/drivers/gpu/drm/exynos/exynos_drm_drv.h
index eaa1966..0eaf5a2 100644
--- a/drivers/gpu/drm/exynos/exynos_drm_drv.h
+++ b/drivers/gpu/drm/exynos/exynos_drm_drv.h
@@ -226,6 +226,7 @@
 struct drm_exynos_file_private {
 	struct exynos_drm_g2d_private	*g2d_priv;
 	struct exynos_drm_ipp_private	*ipp_priv;
+	struct file			*anon_filp;
 };
 
 /*