AMD Steppe Eagle: Add 32-bit Fletcher's Checksum computation

The AMD Platform Security Processor (PSP) requires a Fletcher's
Checksum at the end of the PSP directory.  This code implements
a Fletcher's Checksum by reading bytes from stdin and writes the
bytes back to stdout with a checksum inserted into the byte stream
at the appropriate offset.

This utility is used on PSP binaries during coreboot build.

Include a runtime debug option such that the command:

	fletcher --print <file.bin >file_with_cksum.bin

will print out the computed checksum value for debugging.  The
compile-time debug option is retained that allows -DDEBUG to
be added to the compilation line.  This option has the same
effect as "--print".

Change-Id: I506a479d8204ca4f8267d53aa152ac4b473dbc75
Signed-off-by: Bruce Griffith <Bruce.Griffith@se-eng.com>
Reviewed-on: http://review.coreboot.org/6676
Reviewed-by: WANG Siyuan <wangsiyuanbuaa@gmail.com>
Tested-by: build bot (Jenkins)
Reviewed-by: Zheng Bao <zheng.bao@amd.com>

util/fletcher/Makefile

@@ -0,0 +1,37 @@
+#*****************************************************************************
+#
+# Copyright (c) 2014, Sage Electronic Engineering, LLC
+# All rights reserved.
+#
+# Redistribution and use in source and binary forms, with or without
+# modification, are permitted provided that the following conditions are met:
+#     * Redistributions of source code must retain the above copyright
+#       notice, this list of conditions and the following disclaimer.
+#     * Redistributions in binary form must reproduce the above copyright
+#       notice, this list of conditions and the following disclaimer in the
+#       documentation and/or other materials provided with the distribution.
+#     * Neither the name of Advanced Micro Devices, Inc. nor the names of
+#       its contributors may be used to endorse or promote products derived
+#       from this software without specific prior written permission.
+#
+# THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND
+# ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
+# WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+# DISCLAIMED. IN NO EVENT SHALL ADVANCED MICRO DEVICES, INC. BE LIABLE FOR ANY
+# DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
+# (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
+# LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
+# ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+# (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
+# SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+#
+#*****************************************************************************
+HOSTCC ?= gcc
+
+fletcher_exe : fletcher.c
+	$(HOSTCC) fletcher.c -o fletcher
+
+fletcher : fletcher_exe
+
+clean:
+	@rm -f fletcher.o fletcher fletcher.exe