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/armv7m.h

@@ -171,9 +171,11 @@ struct armv7m_common {
 	struct adiv5_dap dap;
 
 	int fp_feature;
-
 	uint32_t demcr;
 
+	/* stlink is a high level adapter, does not support all functions */
+	bool stlink;
+
 	/* Direct processor core register read and writes */
 	int (*load_core_reg_u32)(struct target *target,
 		enum armv7m_regtype type, uint32_t num, uint32_t *value);