mem-cache: Workaround for setWhenReady assertion

Change 174da8e2da added an assert that
is not satisfiable with current implementation, breaking some
regression tests.

Change-Id: Ibafaf0c51906384364f0b2a4b931f8ec6126d858
Signed-off-by: Daniel R. Carvalho <odanrc@yahoo.com.br>
Reviewed-on: https://gem5-review.googlesource.com/c/14955
Reviewed-by: Giacomo Travaglini <giacomo.travaglini@arm.com>
Reviewed-by: Nikos Nikoleris <nikos.nikoleris@arm.com>
Maintainer: Nikos Nikoleris <nikos.nikoleris@arm.com>

src/mem/cache/cache_blk.hh

@@ -284,7 +284,6 @@ class CacheBlk : public ReplaceableEntry
      */
     void setWhenReady(const Tick tick)
     {
-        assert((whenReady == MaxTick) || (tick >= whenReady));
         assert(tick >= tickInserted);
         whenReady = tick;
     }