tools/vm: add missing Makefile rules

Currently the tools/vm Makefile has a rather arbitrary implicit build
rule; page-types is the first value in TARGETS so lets just build that
one!  Additionally there is no install rule and this is needed for make -C
tools vm_install to work properly.

Provide a more sensible implicit build rule and a new install rule.

Note that the variables names used by the install rule (DESTDIR and
sbindir) are copied from prior-art in tools/power/cpupower.

Link: http://lkml.kernel.org/r/20170113165630.27541-1-daniel.thompson@linaro.org
Signed-off-by: Daniel Thompson <daniel.thompson@linaro.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>