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/gpu-compute/gpu_dyn_inst.hh

@@ -382,7 +382,7 @@ class GPUDynInst : public GPUExecContext
     }
 
     void
-    setRequestFlags(Request *req, bool setMemOrder=true)
+    setRequestFlags(RequestPtr req, bool setMemOrder=true)
     {
         // currently these are the easy scopes to deduce
         if (isPrivateSeg()) {