perf tests arm64: Compile tests unconditionally

In order to subsequently add more tests for the arm64 architecture we
compile the tests target for arm64 systematically.

Further explanation provided by Mark Rutland:

Given prior questions regarding this commit, it's probably worth
spelling things out more explicitly, e.g.

  Currently we only build the arm64/tests directory if
  CONFIG_DWARF_UNWIND is selected, which is fine as the only test we
  have is arm64/tests/dwarf-unwind.o.

  So that we can add more tests to the test directory, let's
  unconditionally build the directory, but conditionally build
  dwarf-unwind.o depending on CONFIG_DWARF_UNWIND.

  There should be no functional change as a result of this patch.

Signed-off-by: Raphael Gault <raphael.gault@arm.com>
Acked-by: Mark Rutland <mark.rutland@arm.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Will Deacon <will.deacon@arm.com>
Cc: linux-arm-kernel@lists.infradead.org
Link: http://lkml.kernel.org/r/20190611125315.18736-2-raphael.gault@arm.com


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