base: Remove negation operator in Flag

There is already a bool conversion operator, so there
is no need to provide a negation operator.

Change-Id: If5f99f8a0bb1707c115d139417aedd47bd162963
Signed-off-by: Daniel R. Carvalho <odanrc@yahoo.com.br>
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/38708
Reviewed-by: Gabe Black <gabe.black@gmail.com>
Maintainer: Bobby R. Bruce <bbruce@ucdavis.edu>
Tested-by: kokoro <noreply+kokoro@google.com>

src/base/debug.hh

@@ -73,7 +73,6 @@ class Flag
     virtual bool status() const = 0;
 
     operator bool() const { return status(); }
-    bool operator!() const { return !status(); }
 
     static void globalEnable();
     static void globalDisable();