target: restructure dap support

- add 'dap create' command to create dap instances
- move all dap subcmmand into the dap instance commands
- keep 'dap info' for convenience
- change all armv7 and armv8 targets to take a dap
  instance instead of a jtag chain position
- restructure tap/dap/target relations, jtag tap no
  longer references the dap, daps are now independently
  created and initialized.
- clean up swd connect
- re-initialize DAP also on JTAG errors (e.g. after reset,
  power cycle)
- update documentation
- update target files

Change-Id: I322cf3969b5407c25d1d3962f9d9b9bc1df067d9
Signed-off-by: Matthias Welwarsky <matthias.welwarsky@sysgo.com>
Reviewed-on: http://openocd.zylin.com/4468
Tested-by: jenkins
Reviewed-by: Matthias Welwarsky <matthias@welwarsky.de>

tcl/target/bcm281xx.cfg

@@ -14,15 +14,17 @@ if { [info exists DAP_TAPID] } {
 	set _DAP_TAPID 0x4ba00477
 }
 
-jtag newtap $_CHIPNAME dap -expected-id $_DAP_TAPID -irlen 4
+jtag newtap $_CHIPNAME cpu -expected-id $_DAP_TAPID -irlen 4
 
 
 # Dual Cortex-A9
 set _TARGETNAME0 $_CHIPNAME.cpu0
 set _TARGETNAME1 $_CHIPNAME.cpu1
 
-target create $_TARGETNAME0 cortex_a -chain-position $_CHIPNAME.dap -coreid 0 -dbgbase 0x3fe10000
-target create $_TARGETNAME1 cortex_a -chain-position $_CHIPNAME.dap -coreid 1 -dbgbase 0x3fe12000
+dap create $_CHIPNAME.dap -chain-position $_CHIPNAME.cpu
+
+target create $_TARGETNAME0 cortex_a -dap $_CHIPNAME.dap -coreid 0 -dbgbase 0x3fe10000
+target create $_TARGETNAME1 cortex_a -dap $_CHIPNAME.dap -coreid 1 -dbgbase 0x3fe12000
 target smp $_TARGETNAME0 $_TARGETNAME1
 
 $_TARGETNAME0 configure -event gdb-attach {