Convert CONFIG_CLOCKS to Kconfig

This converts the following to Kconfig:
   CONFIG_CLOCKS

Signed-off-by: Tom Rini <trini@konsulko.com>
diff --git a/configs/xilinx_zynq_virt_defconfig b/configs/xilinx_zynq_virt_defconfig
index 5bcd17a..e837123 100644
--- a/configs/xilinx_zynq_virt_defconfig
+++ b/configs/xilinx_zynq_virt_defconfig
@@ -27,6 +27,7 @@
 CONFIG_LEGACY_IMAGE_FORMAT=y
 # CONFIG_ARCH_FIXUP_FDT_MEMORY is not set
 CONFIG_USE_PREBOOT=y
+CONFIG_CLOCKS=y
 CONFIG_SPL_STACK_R=y
 CONFIG_SPL_FPGA=y
 CONFIG_SPL_OS_BOOT=y