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>

drivers/video/ipu.h

@@ -253,6 +253,7 @@ struct clk *clk_get_parent(struct clk *clk);
 
 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);

drivers/video/ipu_common.c

@@ -1243,3 +1243,8 @@ int ipu_set_ldb_clock(int rate)
 
 	return 0;
 }
+
+bool ipu_clk_enabled(void)
+{
+	return g_ipu_clk_enabled;
+}

drivers/video/mxc_ipuv3_fb.c

@@ -571,6 +571,9 @@ void ipuv3_fb_shutdown(void)
 	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) {