Convert CONFIG_CMD_GETTIME to Kconfig

This converts the following to Kconfig:
   CONFIG_CMD_GETTIME

Signed-off-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Tom Rini <trini@konsulko.com>
diff --git a/arch/Kconfig b/arch/Kconfig
index 77e1a3e..0682375 100644
--- a/arch/Kconfig
+++ b/arch/Kconfig
@@ -87,6 +87,7 @@
 	select USB_EHCI_HCD
 	select DM_MMC if MMC
 	imply CMD_FPGA_LOADMK
+	imply CMD_GETTIME
 
 config XTENSA
 	bool "Xtensa architecture"