Kconfig: Add CONFIG_HASH to enable hashing API

At present CONFIG_CMD_HASH enables the 'hash' command which also brings
in the hashing API. Some boards may wish to enable the API without the
command. Add a separate CONFIG to permit this.

Signed-off-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Tom Rini <trini@konsulko.com>
diff --git a/cmd/Kconfig b/cmd/Kconfig
index b05e69a..1e3cd02 100644
--- a/cmd/Kconfig
+++ b/cmd/Kconfig
@@ -350,6 +350,7 @@
 
 config CMD_CRC32
 	bool "crc32"
+	select HASH
 	default y
 	help
 	  Compute CRC32.
@@ -998,6 +999,7 @@
 
 config CMD_HASH
 	bool "Support 'hash' command"
+	select HASH
 	help
 	  This provides a way to hash data in memory using various supported
 	  algorithms (such as SHA1, MD5, CRC32). The computed digest can be