sim: Get rid of the now unused System::getPageShift() method.

The other related getPageBytes method is still used for now.

Change-Id: I22e04b47d3932751e03efc0918d44fc1627833bd
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/50353
Reviewed-by: Giacomo Travaglini <giacomo.travaglini@arm.com>
Maintainer: Giacomo Travaglini <giacomo.travaglini@arm.com>
Tested-by: kokoro <noreply+kokoro@google.com>

src/sim/system.hh

@@ -397,11 +397,6 @@ class System : public SimObject, public PCEventScope
      */
     Addr getPageBytes() const { return TheISA::PageBytes; }
 
-    /**
-     * Get the number of bits worth of in-page address for the ISA.
-     */
-    Addr getPageShift() const { return TheISA::PageShift; }
-
     /**
      * The thermal model used for this system (if any).
      */