stm32w: Added sample target configuration for STM32W108 with STLink-V2

As requested, here is the target configuration that I'm using for an
STLink-V2-attached STM32W108C8. For some reason, it only seems to work
with "reset_config trst_only".

Change-Id: Icbff4f83343e1f505d8afdfc53ff6f8b7496cac9
Signed-off-by: Ben Nahill <bnahill@gmail.com>
Reviewed-on: http://openocd.zylin.com/1347
Tested-by: jenkins
Reviewed-by: Freddie Chopin <freddie.chopin@gmail.com>

tcl/target/stm32w108_stlink.cfg

@@ -0,0 +1,23 @@
+#
+# STM32W108xx stlink pseudo target
+#
+
+if { [info exists CHIPNAME] == 0 } {
+   set CHIPNAME stm32w108
+}
+
+if { [info exists CPUTAPID] == 0 } {
+   set CPUTAPID 0x1ba01477
+}
+
+if { [info exists WORKAREASIZE] == 0 } {
+   # 4k -- This should work for all chips, though perhaps not optimally
+   set WORKAREASIZE 0x1000
+}
+
+source [find target/stm32_stlink.cfg]
+
+# Use the flash driver from the EM357
+set _FLASHNAME $_CHIPNAME.flash
+# 64k (0x10000) of flash
+flash bank $_FLASHNAME em357 0x08000000 0x10000 0 0 $_TARGETNAME