AT91SAM4L: handle reset run/halt in SMAP

AT91SAM4L: handle reset run/halt in SMAP

This is a remake of http://openocd.zylin.com/1966
originally written by Angus Gratton <gus@projectgus.com>

ATSAM4L has a "System Manager Access Port" (SMAP) that holds the CPU
in reset if TCK is low when srst (RESET_N) is deasserted.
Without this change any use of sysresetreq or srst locks the chip
in reset state until power is cycled.

A new function smap_reset_deassert is called as reset-deassert-post event handler.
It optionally prepares reset vector catch and SMAP reset is released then.

Change-Id: Iad736357b0f551725befa2b9e00f3bc54504f3d8
Signed-off-by: Tomas Vanek <vanekt@fbl.cz>
Reviewed-on: http://openocd.zylin.com/2604
Tested-by: jenkins
Reviewed-by: Paul Fertser <fercerpav@gmail.com>