configs: stm32f469-disco: Set CYCLIC_MAX_CPU_TIME_US to 50000 for stm32f469-disco

Updating the framebuffer takes quite a long time on this slow patform,
set CYCLIC_MAX_CPU_TIME_US to 50000 for stm32f469-disco to avoid
following cyclic warning:

"cyclic function video_init took too long: 46784us vs 5000us max"

Signed-off-by: Patrice Chotard <patrice.chotard@foss.st.com>
Reviewed-by: Patrick Delaunay <patrick.delaunay@foss.st.com>
diff --git a/configs/stm32f469-discovery_defconfig b/configs/stm32f469-discovery_defconfig
index 9839941..b014476 100644
--- a/configs/stm32f469-discovery_defconfig
+++ b/configs/stm32f469-discovery_defconfig
@@ -14,6 +14,7 @@
 CONFIG_BOOTDELAY=3
 CONFIG_SYS_PBSIZE=1050
 # CONFIG_DISPLAY_CPUINFO is not set
+CONFIG_CYCLIC_MAX_CPU_TIME_US=50000
 CONFIG_MISC_INIT_R=y
 CONFIG_SYS_PROMPT="U-Boot > "
 CONFIG_CMD_IMLS=y