hla_interface: init trst, srst variables.

hla_interface: init trst, srst variables.

  There is an remark in jtag_srst and jtag_trst variables declaration:
  /*
   * JTAG adapters must initialize with TRST and SRST de-asserted
   * (they're negative logic, so that means *high*).  But some
   * hardware doesn't necessarily work that way ... so set things
   * up so that jtag_init() always forces that state.
   */

  but in hla_target such forsing is missed and both variables remains
  uninitialized until "reset" command issued, It prevents target polling
  when connecting to running target.

Change-Id: Ia620d8794cca8ba1403f5c5f24767e730033748a
Signed-off-by: Sergey A. Borshch <sb-sf@users.sourceforge.net>
Reviewed-on: http://openocd.zylin.com/1698
Tested-by: jenkins
Reviewed-by: Spencer Oliver <spen@spen-soft.co.uk>
Reviewed-by: Mathias Küster <kesmtp@freenet.de>