arm: mx5: Add LDB clock config code

Add code to configure PLL4, from which the LDB clock are directly
derived.

Signed-off-by: Marek Vasut <marex@denx.de>
Cc: Stefano Babic <sbabic@denx.de>
diff --git a/arch/arm/include/asm/arch-mx5/clock.h b/arch/arm/include/asm/arch-mx5/clock.h
index 0ecbdee..6f5ca58 100644
--- a/arch/arm/include/asm/arch-mx5/clock.h
+++ b/arch/arm/include/asm/arch-mx5/clock.h
@@ -38,6 +38,7 @@
 	MXC_NFC_CLK,
 	MXC_PERIPH_CLK,
 	MXC_I2C_CLK,
+	MXC_LDB_CLK,
 };
 
 u32 imx_get_uartclk(void);