KVM: selftests: x86: clarify what is reported on KVM_GET_MSRS failure

KVM: selftests: x86: clarify what is reported on KVM_GET_MSRS failure

When KVM_GET_MSRS fail the report looks like

==== Test Assertion Failure ====
  lib/x86_64/processor.c:1089: r == nmsrs
  pid=28775 tid=28775 - Argument list too long
     1	0x000000000040a55f: vcpu_save_state at processor.c:1088 (discriminator 3)
     2	0x00000000004010e3: main at state_test.c:171 (discriminator 4)
     3	0x00007fb8e69223d4: ?? ??:0
     4	0x0000000000401287: _start at ??:?
  Unexpected result from KVM_GET_MSRS, r: 36 (failed at 194)

and it's not obvious that '194' here is the failed MSR index and that
it's printed in hex. Change that.

Suggested-by: Sean Christopherson <sean.j.christopherson@intel.com>
Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>