tools/kvm_stat: add new interactive command 's'

Add new command 's' to modify the update interval. Limited to a maximum of
25.5 sec and a minimum of 0.1 sec, since curses cannot handle longer
and shorter delays respectively.

Signed-off-by: Stefan Raspl <raspl@linux.vnet.ibm.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
diff --git a/tools/kvm/kvm_stat/kvm_stat.txt b/tools/kvm/kvm_stat/kvm_stat.txt
index 2bad6f2..cc019b0 100644
--- a/tools/kvm/kvm_stat/kvm_stat.txt
+++ b/tools/kvm/kvm_stat/kvm_stat.txt
@@ -43,6 +43,8 @@
 
 *r*::	reset stats
 
+*s*::   set update interval
+
 *x*::	toggle reporting of stats for child trace events
 
 Press any other key to refresh statistics immediately.