misc: Substitute pointer to Request with aliased RequestPtr

Every usage of Request* in the code has been replaced with the
RequestPtr alias.  This is a preparing patch for when RequestPtr will be
the typdefed to a smart pointer to Request rather then a raw pointer to
Request.

Change-Id: I73cbaf2d96ea9313a590cdc731a25662950cd51a
Signed-off-by: Giacomo Travaglini <giacomo.travaglini@arm.com>
Reviewed-by: Nikos Nikoleris <nikos.nikoleris@arm.com>
Reviewed-on: https://gem5-review.googlesource.com/10995
Reviewed-by: Anthony Gutierrez <anthony.gutierrez@amd.com>
Reviewed-by: Daniel Carvalho <odanrc@yahoo.com.br>
Maintainer: Anthony Gutierrez <anthony.gutierrez@amd.com>

src/mem/cache/prefetch/queued.cc

@@ -223,7 +223,7 @@ QueuedPrefetcher::insert(AddrPriority &pf_info, bool is_secure)
     }
 
     /* Create a prefetch memory request */
-    Request *pf_req =
+    RequestPtr pf_req =
         new Request(pf_info.first, blkSize, 0, masterId);
 
     if (is_secure) {