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/imx6.cfg

@@ -13,7 +13,7 @@ if { [info exists DAP_TAPID] } {
         set _DAP_TAPID 0x4ba00477
 }
 
-jtag newtap $_CHIPNAME dap -irlen 4 -ircapture 0x01 -irmask 0x0f \
+jtag newtap $_CHIPNAME cpu -irlen 4 -ircapture 0x01 -irmask 0x0f \
         -expected-id $_DAP_TAPID
 
 # SDMA / no IDCODE
@@ -40,7 +40,8 @@ jtag newtap $_CHIPNAME sjc -irlen 5 -ircapture 0x01 -irmask 0x1f \
 # core 2  -  0x82154000
 # core 3  -  0x82156000
 set _TARGETNAME $_CHIPNAME.cpu.0
-target create $_TARGETNAME cortex_a -chain-position $_CHIPNAME.dap \
+dap create $_CHIPNAME.dap -chain-position $_CHIPNAME.cpu
+target create $_TARGETNAME cortex_a -dap $_CHIPNAME.dap \
         -coreid 0 -dbgbase 0x82150000
 
 # some TCK cycles are required to activate the DEBUG power domain