selftests/vDSO: fix runtime errors on LoongArch

selftests/vDSO: fix runtime errors on LoongArch

It could not find __vdso_getcpu and __vdso_gettimeofday when test getcpu
and gettimeofday on LoongArch.

  # make headers && cd tools/testing/selftests/vDSO && make
  # ./vdso_test_getcpu
  Could not find __vdso_getcpu
  # ./vdso_test_gettimeofday
  Could not find __vdso_gettimeofday

One simple way is to add LoongArch case to define version and name, just
like commit d942f231afc0 ("selftests/vDSO: Add riscv getcpu & gettimeofday
test"), but it is not the best way.

Since each architecture has already defined names and versions in
vdso_config.h, it is proper to include vdso_config.h to get version and
name for all archs.

Link: https://lkml.kernel.org/r/20240428030530.24399-3-yangtiezhu@loongson.cn
Signed-off-by: Tiezhu Yang <yangtiezhu@loongson.cn>
Reviewed-by: Muhammad Usama Anjum <usama.anjum@collabora.com>
Tested-by: Muhammad Usama Anjum <usama.anjum@collabora.com>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Kees Cook <keescook@chromium.org>
Cc: Mark Brown <broonie@kernel.org>
Cc: Shuah Khan <skhan@linuxfoundation.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Vincenzo Frascino <vincenzo.frascino@arm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>