gdb/linux-nat: don't memset siginfo on failure in linux_nat_get_siginfo

No caller cares about the value of *SIGINFO on failure.  It's also
documented in the function doc that *SIGINFO is uninitialized (I
understand "untouched") on failure.

Change-Id: I5ef38a5f58e3635e109b919ddf6f827f38f1225a

gdb/linux-nat.c

diff --git a/gdb/linux-nat.c b/gdb/linux-nat.c
index 7b6a1f9..c47b8db 100644
--- a/gdb/linux-nat.c
+++ b/gdb/linux-nat.c
@@ -4446,12 +4446,8 @@ linux_nat_get_siginfo (ptid_t ptid, siginfo_t *siginfo)
 
   errno = 0;
   ptrace (PTRACE_GETSIGINFO, pid, (PTRACE_TYPE_ARG3) 0, siginfo);
-  if (errno != 0)
-    {
-      memset (siginfo, 0, sizeof (*siginfo));
-      return false;
-    }
-  return true;
+
+  return errno == 0;
 }
 
 /* See nat/linux-nat.h.  */