The bit 12 represents "Processor Event Based Sampling Unavailable (RO)" :
	1 = PEBS is not supported.
	0 = PEBS is supported.

A write to this PEBS_UNAVL available bit will bring #GP(0) when guest PEBS
is enabled. Some PEBS drivers in guest may care about this bit.
Signed-off-by: NLike Xu <like.xu@linux.intel.com>
Message-Id: <20220411101946.20262-13-likexu@tencent.com>
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>