mem: Compile tracePacket only when TRACING_ON is defined

If TRACING_ON is not defined (e.g. when building gem5.fast), clang
compilations will fail reporting an unused function.

Change-Id: I959dba6e9fcf74b951e16365077939ae4d4ef924
Signed-off-by: Giacomo Travaglini <giacomo.travaglini@arm.com>
Reviewed-by: Nikos Nikoleris <nikos.nikoleris@arm.com>
Reviewed-on: https://gem5-review.googlesource.com/c/14975
Maintainer: Nikos Nikoleris <nikos.nikoleris@arm.com>
diff --git a/src/mem/abstract_mem.cc b/src/mem/abstract_mem.cc
index b05a99d..581fc14 100644
--- a/src/mem/abstract_mem.cc
+++ b/src/mem/abstract_mem.cc
@@ -289,6 +289,7 @@
     return allowStore;
 }
 
+#if TRACING_ON
 static inline void
 tracePacket(System *sys, const char *label, PacketPtr pkt)
 {
@@ -308,7 +309,6 @@
     DDUMP(MemoryAccess, pkt->getConstPtr<uint8_t>(), pkt->getSize());
 }
 
-#if TRACING_ON
 #   define TRACE_PACKET(A) tracePacket(system(), A, pkt)
 #else
 #   define TRACE_PACKET(A)