perf cs-etm: Detect pid in VMID for kernel running at EL2

perf cs-etm: Detect pid in VMID for kernel running at EL2

The PID of the task could be traced as VMID when the kernel is running
at EL2.  Teach the decoder to look for VMID when the CONTEXTIDR (Arm32)
or CONTEXTIDR_EL1 (Arm64) is invalid but we have a valid VMID.

Signed-off-by: Suzuki K Poulose <suzuki.poulose@arm.com>
Co-developed-by: Leo Yan <leo.yan@linaro.org>
Reviewed-by: Mathieu Poirier <mathieu.poirier@linaro.org>
Cc: Al Grant <al.grant@arm.com>
Cc: Mike Leach <mike.leach@linaro.org>
Link: https://lore.kernel.org/r/20210213113220.292229-6-leo.yan@linaro.org
Link: https://lore.kernel.org/r/20210224164835.3497311-7-mathieu.poirier@linaro.org
Signed-off-by: Leo Yan <leo.yan@linaro.org>
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>