video: ipuv3_fb: skip IPU shutdown if IPU was not enabled before

Boards can skip display interface init using board_video_skip().
If display interface was not initialized (e.g. no ipuv3 framebuffer
registered or IPU clock disabled), booting Linux stops due to the
crash in IPU shutdown function, when accessing IPU registers.
Check IPU clock and skip shutdown if clock is not enabled.

Signed-off-by: Anatolij Gustschin <agust@denx.de>
diff --git a/drivers/video/ipu.h b/drivers/video/ipu.h
index 348be58..ff91d18 100644
--- a/drivers/video/ipu.h
+++ b/drivers/video/ipu.h
@@ -253,6 +253,7 @@
 
 void ipu_dump_registers(void);
 int ipu_probe(void);
+bool ipu_clk_enabled(void);
 
 void ipu_dmfc_init(int dmfc_type, int first);
 void ipu_init_dc_mappings(void);
diff --git a/drivers/video/ipu_common.c b/drivers/video/ipu_common.c
index f8d4488..f259fb9 100644
--- a/drivers/video/ipu_common.c
+++ b/drivers/video/ipu_common.c
@@ -1243,3 +1243,8 @@
 
 	return 0;
 }
+
+bool ipu_clk_enabled(void)
+{
+	return g_ipu_clk_enabled;
+}
diff --git a/drivers/video/mxc_ipuv3_fb.c b/drivers/video/mxc_ipuv3_fb.c
index 0d0a0a9..1ab5cb7 100644
--- a/drivers/video/mxc_ipuv3_fb.c
+++ b/drivers/video/mxc_ipuv3_fb.c
@@ -571,6 +571,9 @@
 	int i;
 	struct ipu_stat *stat = (struct ipu_stat *)IPU_STAT;
 
+	if (!ipu_clk_enabled())
+		return;
+
 	for (i = 0; i < ARRAY_SIZE(mxcfb_info); i++) {
 		struct fb_info *fbi = mxcfb_info[i];
 		if (fbi) {