tools: Fix selftests_install Makefile rule

tools: Fix selftests_install Makefile rule

Fix copy/paste error in selftests_install rule which was copy-pasted
from the clean rule but not properly changed.

Signed-off-by: Kevin Hilman <khilman@linaro.org>
Cc: Bamvor Jian Zhang <bamvor.zhangjian@linaro.org>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Jonathan Cameron <jic23@kernel.org>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Pali Rohar <pali.rohar@gmail.com>
Cc: Pavel Machek <pavel@ucw.cz>
Cc: Roberta Dobrescu <roberta.dobrescu@gmail.com>
Cc: Shuah Khan <shuahkh@osg.samsung.com>
Cc: linaro-kernel@lists.linaro.org
Link: http://lkml.kernel.org/r/1447797261-1775-1-git-send-email-khilman@kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>