[PATCH/AARCH64] Fix hardware break points

[Andrew Pinski <pinskia@gmail.com>]

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I noticed after a fork, gdb would fail with the following message:
Unexpected error setting hardware debug registers

This is because it was trying to setup hardware breakpoint debug
registers but it was passing to ptrace garbage for the registers as
they were not zero'd out.

This fixes the problem by zeroing out the regs variable and now
debugging after a fork works on aarch64.

OK?  Built and tested on aarch64-linux-gnu with no regressions.

Thanks,
Andrew Pinski

ChangeLog:
* aarch64-linux-nat.c (aarch64_linux_set_debug_regs): Zero out regs.

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? .aarch64-linux-nat.c.swp
Index: aarch64-linux-nat.c
===================================================================
RCS file: /cvs/src/src/gdb/aarch64-linux-nat.c,v
retrieving revision 1.4
diff -u -p -r1.4 aarch64-linux-nat.c
--- aarch64-linux-nat.c	14 Feb 2013 13:50:30 -0000	1.4
+++ aarch64-linux-nat.c	27 Jul 2013 20:12:39 -0000
@@ -312,6 +312,7 @@ aarch64_linux_set_debug_regs (const stru
   const CORE_ADDR *addr;
   const unsigned int *ctrl;
 
+  memset (&regs, 0, size(regs));
   iov.iov_base = &regs;
   iov.iov_len = sizeof (regs);
   count = watchpoint ? aarch64_num_wp_regs : aarch64_num_bp_regs;