selftests/vDSO: Add riscv getcpu & gettimeofday test

Enable vDSO getcpu & gettimeofday test for riscv. But only riscv64
supports __vdso_gettimeofday and riscv32 is under development.

VERSION
{
LINUX_4.15 {
global:
__vdso_rt_sigreturn;
__vdso_gettimeofday;
__vdso_clock_gettime;
__vdso_clock_getres;
__vdso_getcpu;
__vdso_flush_icache;
local: *;
};
}

Co-developed-by: haocheng.zy <haocheng.zy@linux.alibaba.com>
Signed-off-by: haocheng.zy <haocheng.zy@linux.alibaba.com>
Suggested-by: Mao Han <han_mao@linux.alibaba.com>
Reviewed-by: Shuah Khan <skhan@linuxfoundation.org>
Signed-off-by: Guo Ren <guoren@linux.alibaba.com>
Signed-off-by: Guo Ren <guoren@kernel.org>
Cc: Paul Walmsley <paul.walmsley@sifive.com>
Cc: Palmer Dabbelt <palmer@dabbelt.com>
Cc: Elliott Hughes <enh@google.com>
Signed-off-by: Shuah Khan <skhan@linuxfoundation.org>

selftests: vdso: Add a selftest for vDSO getcpu()

Provide a very basic selftest for getcpu() which similarly to our existing
test for gettimeofday() looks up the function in the vDSO and prints the
results it gets if the function exists and succeeds.

Signed-off-by: Mark Brown <broonie@kernel.org>
Signed-off-by: Shuah Khan <skhan@linuxfoundation.org>