x86/syscall: skip TF-test if running neither on KVM nor AMD

The syscall TF-test runs syscall on 32-bit mode, which is unsupported by
Intel. As a result, if the test is executed on non-KVM environment and
the system does not have AMD CPU, the test crashes. Skip the test in
such case.

Signed-off-by: Nadav Amit <nadav.amit@gmail.com>
Message-Id: <20210609182945.36849-7-nadav.amit@gmail.com>