mem: Default the SE translating port proxy alloc method to NextPage.

This is what's used in 99% of cases, so it makes sense to make it the
default.

Change-Id: I51535b3387d1c1a0d1d89e77cfca10363388b472
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/29399
Reviewed-by: Matthew Poremba <matthew.poremba@amd.com>
Maintainer: Gabe Black <gabeblack@google.com>
Tested-by: kokoro <noreply+kokoro@google.com>

src/mem/se_translating_port_proxy.hh

@@ -60,7 +60,7 @@ class SETranslatingPortProxy : public TranslatingPortProxy
     bool fixupAddr(Addr addr, BaseTLB::Mode mode) const override;
 
   public:
-    SETranslatingPortProxy(ThreadContext *tc, AllocType alloc,
+    SETranslatingPortProxy(ThreadContext *tc, AllocType alloc=NextPage,
                            Request::Flags _flags=0);
 };