ext: Remove unused bankwiseMode variable

Apple LLVM version 10.0.0 (clang-1000.11.45.2) complains about
unused members variables

Change-Id: If1f2210c09e80b632cb3688aaa7df0594f9e49c9
Reviewed-by: Andreas Sandberg <andreas.sandberg@arm.com>
Reviewed-on: https://gem5-review.googlesource.com/c/13228
Reviewed-by: Nikos Nikoleris <nikos.nikoleris@arm.com>
Reviewed-by: Jason Lowe-Power <jason@lowepower.com>
Maintainer: Jason Lowe-Power <jason@lowepower.com>

ext/drampower/src/libdrampower/LibDRAMPower.h

@@ -82,7 +82,6 @@ class libDRAMPower {
   Data::CommandAnalysis counters;
  private:
   bool includeIoAndTermination;
-  bool bankwiseMode;
   Data:: MemBankWiseParams bwPowerParams;
   // Object of MemoryPowerModel which contains the results
   // Energies(pJ) stored in energy, Powers(mW) stored in power. Number of