Allow transports to override the selected target (hla configs unification)

This should allow to share common configs for both regular access and
high-level adapters.

Use the newly-added functionality in stlink and icdi drivers, amend
the configs accordingly.

Runtime-tested with a TI tm4c123g board.

Change-Id: Ibb88266a4ca25f06f6c073e916c963f017447bad
Signed-off-by: Paul Fertser <fercerpav@gmail.com>
[gus@projectgus.com: context-specific deprecation warnings]
Signed-off-by: Angus Gratton <gus@projectgus.com>
[andrew.smirnov@gmail.com: additional nrf51.cfg mods]
Signed-off-by: Andrey Smirnov <andrew.smirnov@gmail.com>
Tested-by: Andrey Skvortsov <andrej.skvortzov@gmail.com>
Reviewed-on: http://openocd.zylin.com/1664
Tested-by: jenkins
Reviewed-by: Andreas Fritiofson <andreas.fritiofson@gmail.com>

tcl/target/mdr32f9q2i.cfg

@@ -26,7 +26,12 @@ if { [info exists WORKAREASIZE] } {
 if { [info exists CPUTAPID] } {
    set _CPUTAPID $CPUTAPID
 } else {
-   set _CPUTAPID 0x4ba00477
+   if { [using_jtag] } {
+      set _CPUTAPID 0x4ba00477
+   } {
+      # SWD IDCODE
+      set _CPUTAPID 0x2ba01477
+   }
 }
 swj_newdap $_CHIPNAME cpu -irlen 4 -ircapture 0x1 -irmask 0xf -expected-id $_CPUTAPID
 
@@ -50,6 +55,8 @@ if {[using_jtag]} {
    jtag_ntrst_delay 100
 }
 
-# if srst is not fitted use SYSRESETREQ to
-# perform a soft reset
-cortex_m reset_config sysresetreq
+if {![using_hla]} {
+   # if srst is not fitted use SYSRESETREQ to
+   # perform a soft reset
+   cortex_m reset_config sysresetreq
+}