KVM: selftests: Check for _both_ XTILE data and cfg in AMX test

Check for _both_ XTILE data and cfg support in the AMX test instead of
checking for _either_ feature.  Practically speaking, no sane CPU or vCPU
will support one but not the other, but the effective "or" behavior is
subtle and technically incorrect.

Signed-off-by: Sean Christopherson <seanjc@google.com>
Link: https://lore.kernel.org/r/20220614200707.3315957-11-seanjc@google.com