buildsystem: Make CPU microcode updating more configurable

This patch aims to improve the microcode in CBFS handling that was
brought by the last patches from Stefan and the Chromium team.

Choices in Kconfig
  - 1) Generate microcode from tree (default)
  - 2) Include external microcode file
  - 3) Do not put microcode in CBFS

The idea is to give the user full control over including non-free
blobs in the final ROM image.

MICROCODE_INCLUDE_PATH Kconfig variable is eliminated. Microcode
is handled by a special class, cpu_microcode, as such:

cpu_microcode-y += microcode_file.c

MICROCODE_IN_CBFS should, in the future, be eliminated. Right now it is
needed by intel microcode updating. Once all intel cpus are converted to
cbfs updating, this variable can go away.

These files are then compiled and assembled into a binary CBFS file.
The advantage of doing it this way versus the current method is that
  1) The rule is CPU-agnostic
  2) Gives user more control over if and how to include microcode blobs
  3) The rules for building the microcode binary are kept in
   src/cpu/Makefile.inc, and thus would not clobber the other makefiles,
   which are already overloaded and very difficult to navigate.

Change-Id: I38d0c9851691aa112e93031860e94895857ebb76
Signed-off-by: Alexandru Gagniuc <mr.nuke.me@gmail.com>
Reviewed-on: http://review.coreboot.org/1245
Tested-by: build bot (Jenkins)
Reviewed-by: Anton Kochkov <anton.kochkov@gmail.com>
Reviewed-by: Patrick Georgi <patrick@georgi-clan.de>

src/cpu/intel/model_206ax/Kconfig

@@ -12,7 +12,7 @@ config CPU_SPECIFIC_OPTIONS
 	select SSE2
 	select UDELAY_LAPIC
 	select SMM_TSEG
-	select MICROCODE_IN_CBFS
+	select CPU_MICROCODE_IN_CBFS
 	#select AP_IN_SIPI_WAIT
 	select TSC_SYNC_MFENCE
 

src/cpu/intel/model_206ax/Makefile.inc

@@ -5,4 +5,6 @@ ramstage-$(CONFIG_GENERATE_ACPI_TABLES) += acpi.c
 
 smm-$(CONFIG_HAVE_SMI_HANDLER) += finalize.c
 
+cpu_microcode-$(CONFIG_CPU_MICROCODE_CBFS_GENERATE)  += microcode_blob.c
+
 cpu_incs += $(src)/cpu/intel/model_206ax/cache_as_ram.inc

src/cpu/intel/model_206ax/microcode_blob.c

@@ -0,0 +1,22 @@
+/*
+ * This file is part of the coreboot project.
+ *
+ * Copyright (C) 2012 The ChromiumOS Authors.  All rights reserved.
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; version 2 of the License.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
+ */
+
+unsigned microcode[] = {
+#include "microcode_blob.h"
+};