perf tools: Really install manpages via 'make install-man'

Target install-man builds them but forget to install.

Signed-off-by: Konstantin Khlebnikov <khlebnikov@yandex-team.ru>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Borislav Petkov <borislav.petkov@amd.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Fixes: af3df2cf ("perf tools: Try to build Documentation when installing")
Link: http://lkml.kernel.org/r/150322915300.129715.13645857235229756834.stgit@buzz


Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>