Replace memset 0 with initializers.

Test: Compiles and bionic unit tests pass.
Change-Id: I94e178c56d958beeb1c484e4d52d61df022189e8
diff --git a/tests/sys_ptrace_test.cpp b/tests/sys_ptrace_test.cpp
index 499adbb..1f9c2a2 100644
--- a/tests/sys_ptrace_test.cpp
+++ b/tests/sys_ptrace_test.cpp
@@ -116,8 +116,7 @@
   ASSERT_EQ(0, ptrace(PTRACE_SETHBPREGS, child, -1, &address)) << strerror(errno);
   ASSERT_EQ(0, ptrace(PTRACE_SETHBPREGS, child, -2, &control)) << strerror(errno);
 #else // aarch64
-  user_hwdebug_state dreg_state;
-  memset(&dreg_state, 0, sizeof dreg_state);
+  user_hwdebug_state dreg_state = {};
   dreg_state.dbg_regs[0].addr = address;
   dreg_state.dbg_regs[0].ctrl = control;
 
@@ -304,8 +303,7 @@
   ASSERT_EQ(0, ptrace(PTRACE_SETHBPREGS, child, 1, &address)) << strerror(errno);
   ASSERT_EQ(0, ptrace(PTRACE_SETHBPREGS, child, 2, &control)) << strerror(errno);
 #else  // aarch64
-  user_hwdebug_state dreg_state;
-  memset(&dreg_state, 0, sizeof dreg_state);
+  user_hwdebug_state dreg_state = {};
   dreg_state.dbg_regs[0].addr = reinterpret_cast<uintptr_t>(address);
   dreg_state.dbg_regs[0].ctrl = control;