stlink: add armv7m stlink handling

This enables us to better handle some of the low level functions that the
stlink does not support. It also enables us to share a few more of the
standard cortex_m3 functions if necessary.

Change-Id: I7a2c57450122012ec189245d8879d8967913e00e
Signed-off-by: Spencer Oliver <spen@spen-soft.co.uk>
Reviewed-on: http://openocd.zylin.com/637
Tested-by: jenkins

src/target/stm32_stlink.c

@@ -278,6 +278,7 @@ static int stm32_stlink_init_arch_info(struct target *target,
 	armv7m->store_core_reg_u32 = stm32_stlink_store_core_reg_u32;
 
 	armv7m->examine_debug_reason = stm32_stlink_examine_debug_reason;
+	armv7m->stlink = true;
 
 	return ERROR_OK;
 }