samples: mei: use hostprogs kbuild constructs

Use hostprogs kbuild constructs to compile
mei sample program mei-amt-version

Add CONFIG_SAMPLE_INTEL_MEI option to enable/disable
the feature.
Signed-off-by: Tomas Winkler <tomas.winkler@intel.com>
Link: https://lore.kernel.org/r/20191010132710.4075-1-tomas.winkler@intel.comSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

samples/Kconfig

@@ -169,4 +169,11 @@ config SAMPLE_VFS
 	  as mount API and statx().  Note that this is restricted to the x86
 	  arch whilst it accesses system calls that aren't yet in all arches.
 
+config SAMPLE_INTEL_MEI
+	bool "Build example program working with intel mei driver"
+	depends on INTEL_MEI
+	help
+	  Build a sample program to work with mei device.
+
+
 endif # SAMPLES

samples/Makefile

@@ -20,3 +20,4 @@ obj-$(CONFIG_SAMPLE_TRACE_PRINTK)	+= trace_printk/
 obj-$(CONFIG_VIDEO_PCI_SKELETON)	+= v4l/
 obj-y					+= vfio-mdev/
 subdir-$(CONFIG_SAMPLE_VFS)		+= vfs
+obj-$(CONFIG_SAMPLE_INTEL_MEI)		+= mei/

samples/mei/Makefile

 # SPDX-License-Identifier: GPL-2.0
-CC := $(CROSS_COMPILE)gcc
-CFLAGS := -I../../usr/include
+# Copyright (c) 2012-2019, Intel Corporation. All rights reserved.
 
-PROGS := mei-amt-version
+hostprogs-y := mei-amt-version
 
-all: $(PROGS)
+HOSTCFLAGS_mei-amt-version.o += -I$(objtree)/usr/include
 
-clean:
-	rm -fr $(PROGS)
+always := $(hostprogs-y)
+
+all: mei-amt-version