stm32f429: use 180 MHz system clock

Mainline Linux kernel commit
338a6aaabc02fa63b70441dd0e1b70aea64673c6 (ARM: dts: Introduce
STM32F429 MCU) in arch/arm/boot/dts/stm32f429.dtsi
requires U-Boot to set system clock to 180 MHz.

Signed-off-by: Antonio Borneo <borneo.antonio@gmail.com>
To: Albert Aribaud <albert.u.boot@aribaud.net>
To: Tom Rini <trini@konsulko.com>
To: Kamil Lulko <rev13@wp.pl>
Cc: u-boot@lists.denx.de
diff --git a/include/configs/stm32f429-discovery.h b/include/configs/stm32f429-discovery.h
index f9807db..1ac3db6 100644
--- a/include/configs/stm32f429-discovery.h
+++ b/include/configs/stm32f429-discovery.h
@@ -62,6 +62,8 @@
 
 #define CONFIG_STM32_HSE_HZ		8000000
 
+#define CONFIG_SYS_CLK_FREQ		180000000 /* 180 MHz */
+
 #define CONFIG_SYS_HZ_CLOCK		1000000	/* Timer is clocked at 1MHz */
 
 #define CONFIG_CMDLINE_TAG