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/common/Kconfig b/common/Kconfig
index 1879aef..5c39663 100644
--- a/common/Kconfig
+++ b/common/Kconfig
@@ -493,4 +493,16 @@
 
 endmenu
 
+menu "Security support"
+
+config HASH
+	bool # "Support hashing API (SHA1, SHA256, etc.)"
+	help
+	  This provides a way to hash data in memory using various supported
+	  algorithms (such as SHA1, MD5, CRC32). The API is defined in hash.h
+	  and the algorithms it supports are defined in common/hash.c. See
+	  also CMD_HASH for command-line access.
+
+endmenu
+
 source "common/spl/Kconfig"