perf intel-pt: Adjust sample flags for VM-Exit

perf intel-pt: Adjust sample flags for VM-Exit

Use the change of NR to detect whether an asynchronous branch is a VM-Exit.

Note VM-Entry is determined from the vmlaunch or vmresume instruction,
in which case, sample flags will show "VMentry" even if the VM-Entry fails.

Signed-off-by: Adrian Hunter <[email protected]>
Acked-by: Andi Kleen <[email protected]>
Cc: Alexander Shishkin <[email protected]>
Cc: Jiri Olsa <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Arnaldo Carvalho de Melo <[email protected]>