drm/exynos: check NV12M format specific to Exynos properly

this patch adds buf_cnt variable in exynos_drm_fb structure and
that means a buffer count to drm framebuffer and also adds two
functions to get/set the buffer count from/to exynos_drm_fb structure.
if pixel format is not DRM_FORMAT_NV12MT then it gets a buffer count
to drm framebuffer refering to mode_cmd->handles and offsets.
but when booted, the buffer count will always be 1 because pixel
format of console framebuffer is RGB format.

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_fbdev.c b/drivers/gpu/drm/exynos/exynos_drm_fbdev.c
index f4ac433..d7205f8 100644
--- a/drivers/gpu/drm/exynos/exynos_drm_fbdev.c
+++ b/drivers/gpu/drm/exynos/exynos_drm_fbdev.c
@@ -79,6 +79,9 @@
 		return -EFAULT;
 	}
 
+	/* buffer count to framebuffer always is 1 at booting time. */
+	exynos_drm_fb_set_buf_cnt(fb, 1);
+
 	offset = fbi->var.xoffset * (fb->bits_per_pixel >> 3);
 	offset += fbi->var.yoffset * fb->pitches[0];