Convert CONFIG_CMD_HASH to Kconfig

This converts the following to Kconfig:
   CONFIG_CMD_HASH

Signed-off-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Tom Rini <trini@konsulko.com>
[trini: Rework slightly, enable on some boards again]
Signed-off-by: Tom Rini <trini@konsulko.com>
diff --git a/arch/Kconfig b/arch/Kconfig
index 0682375..ed6b6a0 100644
--- a/arch/Kconfig
+++ b/arch/Kconfig
@@ -68,6 +68,7 @@
 	select DM_SPI
 	select DM_GPIO
 	select DM_MMC
+	imply CMD_HASH
 
 config SH
 	bool "SuperH architecture"