kvm_stat: Add RESET support for perf event ioctl

kvm_stat: Add RESET support for perf event ioctl

While running kvm_stat using tracepoint on ARM64 hardware (e.g. "kvm_stat
-1 -t"), the initial values of some kvm_userspace_exit counters were found
to be very suspecious. For instance the tracing tool showed that S390_TSCH
was called many times on ARM64 machine, which apparently was wrong.

This patch adds RESET ioctl support for perf monitoring. Before calling
ioctl to enable a perf event, this patch resets the counter first. With
this patch, the init counter values become correct on ARM64 hardware.

Example:

==== before patch ====
kvm_userspace_exit(S390_SIEIC)      1426         0
kvm_userspace_exit(S390_TSCH)       339         0

==== after patch ====
kvm_userspace_exit(S390_SIEIC)         0         0
kvm_userspace_exit(S390_TSCH)         0         0

Signed-off-by: Wei Huang <[email protected]>