Add support for SHA384 and SHA512

The current recommendation for best security practice from the US government
is to use SHA384 for TOP SECRET [1].

This patch adds support for SHA384 and SHA512 in the hash command, and also
allows FIT images to be hashed with these algorithms, and signed with
sha384,rsaXXXX and sha512,rsaXXXX

The SHA implementation is adapted from the linux kernel implementation.

[1] Commercial National Security Algorithm Suite
http://www.iad.gov/iad/programs/iad-initiatives/cnsa-suite.cfm

Signed-off-by: Reuben Dowle <reuben.dowle@4rf.com>
diff --git a/Kconfig b/Kconfig
index 0e7ccc0..34a88ebe 100644
--- a/Kconfig
+++ b/Kconfig
@@ -358,12 +358,26 @@
 	help
 	  Enable this to support SHA256 checksum of FIT image contents. A
 	  SHA256 checksum is a 256-bit (32-byte) hash value used to check that
-	  the image contents have not been corrupted. SHA256 is recommended
-	  for use in secure applications since (as at 2016) there is no known
-	  feasible attack that could produce a 'collision' with differing
-	  input data. Use this for the highest security. Note that only the
-	  SHA256 variant is supported: SHA512 and others are not currently
-	  supported in U-Boot.
+	  the image contents have not been corrupted.
+
+config FIT_ENABLE_SHA384_SUPPORT
+	bool "Support SHA384 checksum of FIT image contents"
+	default n
+	select SHA384
+	help
+	  Enable this to support SHA384 checksum of FIT image contents. A
+	  SHA384 checksum is a 384-bit (48-byte) hash value used to check that
+	  the image contents have not been corrupted. Use this for the highest
+	  security.
+
+config FIT_ENABLE_SHA512_SUPPORT
+	bool "Support SHA512 checksum of FIT image contents"
+	default n
+	select SHA512
+	help
+	  Enable this to support SHA512 checksum of FIT image contents. A
+	  SHA512 checksum is a 512-bit (64-byte) hash value used to check that
+	  the image contents have not been corrupted.
 
 config FIT_SIGNATURE
 	bool "Enable signature verification of FIT uImages"