fault_handler : debug output sp in hex and not decimal.

Easier to compare against hex values in tombstones and debuggerd
dumps.

Change-Id: I4a4512ea1ce5872fdb6b41e824fa3475dfcfb71d
diff --git a/runtime/arch/arm/fault_handler_arm.cc b/runtime/arch/arm/fault_handler_arm.cc
index 90b0d53..d81e0a9 100644
--- a/runtime/arch/arm/fault_handler_arm.cc
+++ b/runtime/arch/arm/fault_handler_arm.cc
@@ -70,7 +70,7 @@
   struct ucontext* uc = reinterpret_cast<struct ucontext*>(context);
   struct sigcontext *sc = reinterpret_cast<struct sigcontext*>(&uc->uc_mcontext);
   *out_sp = static_cast<uintptr_t>(sc->arm_sp);
-  VLOG(signals) << "sp: " << *out_sp;
+  VLOG(signals) << "sp: " << std::hex << *out_sp;
   if (*out_sp == 0) {
     return;
   }