KVM: selftests: Assert that both XTILE{CFG,DATA} are XSAVE-enabled

Assert that both XTILE{CFG,DATA} are written and read back via XSETBV and
XGETBV respectively.  The original check in amx_test only ensures at least
one of the XTILE bits are set, XTILECFG or XTILEDATA, when it really
should be checking that both are set.

Fixes: bf70636d ("selftest: kvm: Add amx selftest")
Signed-off-by: Aaron Lewis <aaronlewis@google.com>
Signed-off-by: Mingwei Zhang <mizhang@google.com>
Link: https://lore.kernel.org/r/20230221163655.920289-11-mizhang@google.com


[sean: massage changelog]
Signed-off-by: Sean Christopherson <seanjc@google.com>