perf build: Add arch s390 objects building

Move the s390 arch objects building under build framework to be included
in the libperf build object.
Signed-off-by: Jiri Olsa <jolsa@kernel.org>
Tested-by: Sukadev Bhattiprolu <sukadev@linux.vnet.ibm.com>
Tested-by: Will Deacon <will.deacon@arm.com>
Cc: Alexis Berlemont <alexis.berlemont@gmail.com>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Corey Ashford <cjashfor@linux.vnet.ibm.com>
Cc: David Ahern <dsahern@gmail.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Stephane Eranian <eranian@google.com>
Link: http://lkml.kernel.org/n/tip-8f5tlfwegkirhir2ffz8nw3i@git.kernel.orgSigned-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

tools/perf/arch/s390/Build

+libperf-y += util/

tools/perf/arch/s390/Makefile

 ifndef NO_DWARF
 PERF_HAVE_DWARF_REGS := 1
-LIB_OBJS += $(OUTPUT)arch/$(ARCH)/util/dwarf-regs.o
 endif
-LIB_OBJS += $(OUTPUT)arch/$(ARCH)/util/header.o
 HAVE_KVM_STAT_SUPPORT := 1
-LIB_OBJS += $(OUTPUT)arch/$(ARCH)/util/kvm-stat.o

tools/perf/arch/s390/util/Build

+libperf-y += header.o
+libperf-y += kvm-stat.o
+
+libperf-$(CONFIG_DWARF) += dwarf-regs.o