sim: Fix initialization of ticksClkGated distribution

The third init argument is the bucket size. This should be evaluated
according to the following formula:

bucket size = (max - min + 1.0) / #buckets

Current initialization is not taking into considering the minimum value
(and the +1 offset)

Change-Id: Ie4b8dd7e26d3db60288ab1715ff1b7f0f4fe419e
Signed-off-by: Giacomo Travaglini <giacomo.travaglini@arm.com>
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/41413
Reviewed-by: Jason Lowe-Power <power.jg@gmail.com>
Maintainer: Jason Lowe-Power <power.jg@gmail.com>
Tested-by: kokoro <noreply+kokoro@google.com>

src/sim/power_state.cc

@@ -245,7 +245,8 @@ PowerState::PowerStateStats::regStats()
     // Each sample is time in ticks
     unsigned num_bins = std::max(p.clk_gate_bins, 10U);
     ticksClkGated
-        .init(p.clk_gate_min, p.clk_gate_max, (p.clk_gate_max / num_bins))
+        .init(p.clk_gate_min, p.clk_gate_max,
+            (p.clk_gate_max - p.clk_gate_min + 1.0) / num_bins)
         .flags(pdf | nozero | nonan)
         ;