flash: add stm32f3x support

add support for the new stm32f3x family from stmicro:
http://www.st.com/stm32f3

Change-Id: Icd1db95bb2767d9c0ecef24deefa92b4fdaa4f14
Signed-off-by: Spencer Oliver <spen@spen-soft.co.uk>
Reviewed-on: http://openocd.zylin.com/735
Tested-by: jenkins
Reviewed-by: Freddie Chopin <freddie.chopin@gmail.com>
Reviewed-by: Andreas Fritiofson <andreas.fritiofson@gmail.com>

tcl/target/stm32f3x_stlink.cfg

@@ -0,0 +1,20 @@
+#
+# STM32f3x stlink pseudo target
+#
+
+if { [info exists CHIPNAME] == 0 } {
+   set CHIPNAME stm32f3x
+}
+
+if { [info exists CPUTAPID] == 0 } {
+   set CPUTAPID 0x1ba01477
+}
+
+if { [info exists WORKAREASIZE] == 0 } {
+   set WORKAREASIZE 0x4000
+}
+
+source [find target/stm32_stlink.cfg]
+
+set _FLASHNAME $_CHIPNAME.flash
+flash bank $_FLASHNAME stm32f1x 0 0 0 0 $_TARGETNAME