base-stats: Fix Watt Unit

Watt had two implementations. Since having the unit
printed as Watt is more relevant than as Joule/Second,
keep the class.

Change-Id: Ic9ae755115e2eca94492f3d5b11245db9fe42bb6
Signed-off-by: Daniel R. Carvalho <odanrc@yahoo.com.br>
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/43006
Reviewed-by: Bobby R. Bruce <bbruce@ucdavis.edu>
Maintainer: Bobby R. Bruce <bbruce@ucdavis.edu>
Tested-by: kokoro <noreply+kokoro@google.com>
diff --git a/src/base/stats/units.hh b/src/base/stats/units.hh
index 5b785b4..b2dfefa 100644
--- a/src/base/stats/units.hh
+++ b/src/base/stats/units.hh
@@ -47,10 +47,9 @@
 #define UNIT_RATE(T1, T2) Stats::Units::Rate<T1, T2>::get()
 #define UNIT_RATIO Stats::Units::Ratio::get()
 #define UNIT_COUNT Stats::Units::Count::get()
+#define UNIT_WATT Stats::Units::Watt::get()
 #define UNIT_UNSPECIFIED Stats::Units::Unspecified::get()
 
-#define UNIT_WATT UNIT_RATE(Stats::Units::Joule, Stats::Units::Second)
-
 namespace Stats {
 
 /**