video, ipu: make ldb clock frequency overwritable through board code

the ldb clock can be setup in board code (for example set through PLL5).
Update the ldb_clock rate also through board code.

This should be removed, if a clock framework is availiable.

Signed-off-by: Heiko Schocher <hs@denx.de>
Tested-by: Eric Nelson <eric.nelson@boundarydevices.com>

arch/arm/include/asm/imx-common/video.h

@@ -26,4 +26,5 @@ extern struct display_info_t const displays[];
 extern size_t display_count;
 #endif
 
+int ipu_set_ldb_clock(int rate);
 #endif

drivers/video/ipu.h

@@ -265,5 +265,4 @@ int ipu_dp_init(ipu_channel_t channel, uint32_t in_pixel_fmt,
 void ipu_dp_uninit(ipu_channel_t channel);
 void ipu_dp_dc_disable(ipu_channel_t channel, unsigned char swap);
 ipu_color_space_t format_to_colorspace(uint32_t fmt);
-
 #endif

drivers/video/ipu_common.c

@@ -1198,3 +1198,11 @@ ipu_color_space_t format_to_colorspace(uint32_t fmt)
 	}
 	return RGB;
 }
+
+/* should be removed when clk framework is availiable */
+int ipu_set_ldb_clock(int rate)
+{
+	ldb_clk.rate = rate;
+
+	return 0;
+}