nrf51: Implement the support for Nordic's nRF51 devices

Add support for Nordic's nRF51 chip series. Tested with nRF51822.

Change-Id: Id70f6fd76888cc595a353aefb84d25c4cd325d7d
Signed-off-by: Andrey Smirnov <andrew.smirnov@gmail.com>
Reviewed-on: http://openocd.zylin.com/1945
Tested-by: jenkins
Reviewed-by: Andrey Yurovsky <yurovsky@gmail.com>
Reviewed-by: Spencer Oliver <spen@spen-soft.co.uk>

tcl/target/nrf51_stlink.tcl

@@ -0,0 +1,70 @@
+#
+# script for Nordic nRF51 series, a CORTEX-M0 chip
+#
+
+source [find target/swj-dp.tcl]
+
+if { [info exists CHIPNAME] } {
+   set _CHIPNAME $CHIPNAME
+} else {
+   set _CHIPNAME nrf51
+}
+
+if { [info exists ENDIAN] } {
+   set _ENDIAN $ENDIAN
+} else {
+   set _ENDIAN little
+}
+
+# Work-area is a space in RAM used for flash programming
+# By default use 2kB
+if { [info exists WORKAREASIZE] } {
+   set _WORKAREASIZE $WORKAREASIZE
+} else {
+   set _WORKAREASIZE 0x800
+}
+
+if { [info exists CPUTAPID] } {
+   set _CPUTAPID $CPUTAPID
+} else {
+   set _CPUTAPID 0x0bb11477
+}
+
+if { [info exists TRANSPORT] } {
+   set _TRANSPORT $TRANSPORT
+   if { $TRANSPORT == "hla_jtag" } {
+      if { [info exists CPUTAPID] == 0 } {
+         # jtag requires us to use the jtag tap id
+         set _CPUTAPID 0x3ba00477
+      }
+   }
+} else {
+   set _TRANSPORT hla_swd
+}
+
+# add deprecated transport name check
+if { $_TRANSPORT == "stlink_swd" } {
+	set _TRANSPORT "hla_swd"
+	echo "DEPRECATED! use 'hla_swd' transport not 'stlink_swd'"
+}
+
+if { $_TRANSPORT == "stlink_jtag" } {
+	set _TRANSPORT "hla_jtag"
+	echo "DEPRECATED! use 'hla_jtag' transport not 'stlink_jtag'"
+}
+# end deprecated checks
+
+transport select $_TRANSPORT
+hla newtap $_CHIPNAME cpu -expected-id $_CPUTAPID
+
+set _TARGETNAME $_CHIPNAME.cpu
+target create $_TARGETNAME hla_target -chain-position $_TARGETNAME
+
+$_TARGETNAME configure -work-area-phys 0x20000000 -work-area-size $_WORKAREASIZE -work-area-backup 0
+
+# The chip supports standard ARM/Cortex-M0 SYSRESETREQ signal, so for
+# non-"hla" targets it would be useful to have the following in the config.
+# cortex_m reset_config sysresetreq
+
+set _FLASHNAME $_CHIPNAME.flash
+flash bank $_FLASHNAME nrf51 0x00000000 0 1 1 $_TARGETNAME