selftests: Move networking/timestamping from Documentation

Remove networking from Documentation Makefile to move the test to
selftests. Update networking/timestamping Makefile to work under
selftests. These tests will not be run as part of selftests suite
and will not be included in install targets. They can be built and
run separately for now.

This is part of the effort to move runnable code from Documentation.
Acked-by: Jonathan Corbet <corbet@lwn.net>
Signed-off-by: Shuah Khan <shuahkh@osg.samsung.com>

Documentation/Makefile

 subdir-y := accounting auxdisplay blackfin \
-	laptops mic misc-devices \
-	networking pcmcia timers watchdog
+	laptops mic misc-devices pcmcia timers watchdog

Documentation/networking/Makefile

-subdir-y := timestamping

Documentation/networking/timestamping/Makefile

-# To compile, from the source root
-#
-#    make headers_install
-#    make M=documentation
-
-# List of programs to build
-hostprogs-y := hwtstamp_config timestamping txtimestamp
-
-# Tell kbuild to always build the programs
-always := $(hostprogs-y)
-
-HOSTCFLAGS_timestamping.o += -I$(objtree)/usr/include
-HOSTCFLAGS_txtimestamp.o += -I$(objtree)/usr/include
-HOSTCFLAGS_hwtstamp_config.o += -I$(objtree)/usr/include

tools/testing/selftests/networking/timestamping/Makefile

+TEST_PROGS := hwtstamp_config timestamping txtimestamp
+
+all: $(TEST_PROGS)
+
+include ../../lib.mk
+
+clean:
+	rm -fr $(TEST_PROGS)