Convert CONFIG_CPU_FREQ_HZ to Kconfig

This converts the following to Kconfig:
   CONFIG_CPU_FREQ_HZ

Cc: Michal Simek <monstr@monstr.eu>
Signed-off-by: Tom Rini <trini@konsulko.com>
diff --git a/arch/arm/mach-zynqmp-r5/Kconfig b/arch/arm/mach-zynqmp-r5/Kconfig
index 5e01754..f14514b 100644
--- a/arch/arm/mach-zynqmp-r5/Kconfig
+++ b/arch/arm/mach-zynqmp-r5/Kconfig
@@ -21,6 +21,12 @@
 	  Based on this option include/configs/<CONFIG_SYS_CONFIG_NAME>.h header
 	  will be used for board configuration.
 
+config CPU_FREQ_HZ
+	int "CPU frequency"
+	default 800000000
+	help
+	  The value, in Hz, that the CPU clock is running at.
+
 config SYS_MALLOC_F_LEN
 	default 0x600