topic: add reset functions for SWD

topic: add reset functions for SWD

Add swd_init_reset and swd_add_reset.
Add adapter_assert_reset and adapter_deassert_reset, and call them instead
of JTAG reset functions.

Change-Id: Ib2551c6fbb45513e0ae0dc331cfe3ee3f922298a
Signed-off-by: Simon Qian <simonqian.openocd@gmail.com>
Reviewed-on: http://openocd.zylin.com/526
Tested-by: jenkins
Reviewed-by: Freddie Chopin <freddie.chopin@gmail.com>
Reviewed-by: Spencer Oliver <spen@spen-soft.co.uk>