tools: PCI: Change pcitest compiling process

Change tool compiling process in order to be build using the same
mechanism used in other linux tools (e.g. iio, perf, etc). This will
allow in future the buildroot tool to build and integrate this tool in
a more expeditious way.

Update documentation accordingly.

Signed-off-by: Gustavo Pimentel <gustavo.pimentel@synopsys.com>
Signed-off-by: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
Reviewed-by: Kishon Vijay Abraham I <kishon@ti.com>

Documentation/PCI/endpoint/pci-test-howto.txt

@@ -99,17 +99,20 @@ Note that the devices listed here correspond to the value populated in 1.4 above
 2.2 Using Endpoint Test function Device
 
 pcitest.sh added in tools/pci/ can be used to run all the default PCI endpoint
-tests. Before pcitest.sh can be used pcitest.c should be compiled using the
-following commands.
+tests. To compile this tool the following commands should be used:
 
-	cd <kernel-dir>
-	make headers_install ARCH=arm
-	arm-linux-gnueabihf-gcc -Iusr/include tools/pci/pcitest.c -o pcitest
-	cp pcitest  <rootfs>/usr/sbin/
-	cp tools/pci/pcitest.sh <rootfs>
+	# cd <kernel-dir>
+	# make -C tools/pci
+
+or if you desire to compile and install in your system:
+
+	# cd <kernel-dir>
+	# make -C tools/pci install
+
+The tool and script will be located in <rootfs>/usr/bin/
 
 2.2.1 pcitest.sh Output
-	# ./pcitest.sh
+	# pcitest.sh
 	BAR tests
 
 	BAR0:           OKAY