i386/kvm: correct the meaning of '0xffffffff' value for hv-spinlocks

i386/kvm: correct the meaning of '0xffffffff' value for hv-spinlocks

Hyper-V TLFS prior to version 6.0 had a mistake in it: special value
'0xffffffff' for CPUID 0x40000004.EBX was called 'never to retry', this
looked weird (like why it's not '0' which supposedly have the same effect?)
but nobody raised the question. In TLFS version 6.0 the mistake was
corrected to 'never notify' which sounds logical. Fix QEMU accordingly.

Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com>
Message-Id: <20200515114847.74523-1-vkuznets@redhat.com>
Signed-off-by: Eduardo Habkost <ehabkost@redhat.com>