cmsis-dap: add initial cmsis-dap support

This is based on work from:
https://github.com/TheShed/OpenOCD-CMSIS-DAP/tree/cmsis-dap

Main changes include moving over to using HIDAPI rather than libusb-1.0
and cleaning up to merge into master. Support for reset using srst has
also been added.

It has been tested on all the mbed boards as well as the Freedom board
from Freescale. These boards only implement SWD mode, however JTAG mode
has been tested with a Keil ULINK2 and a stm32 target - but requires a lot
more work.

Change-Id: I96d5ee1993bc9c0526219ab754c5aad3b55d812d
Signed-off-by: Spencer Oliver <spen@spen-soft.co.uk>
Signed-off-by: Andrey Yurovsky <yurovsky@gmail.com>
Reviewed-on: http://openocd.zylin.com/1542
Tested-by: jenkins

src/jtag/swd.h

@@ -110,11 +110,17 @@ struct swd_driver {
 	  */
 	 int (*write_reg)(uint8_t cmd, uint32_t value);
 
-	/* XXX START WITH enough to:
-	 *	init (synch mode, WCR)
-	 *		for async, TRN > 1
-	 *	read IDCODE from DP
-	 */
+	 /**
+	  * Synchronous block read of an AP or DP register.
+	  *
+	  * @param cmd with APnDP/RnW/addr/parity bits
+	  * @param number of reads from register to be executed
+	  * @param buffer to store data read from register
+	  *
+	  * @return SWD_ACK_* code for the transaction
+	  *		or (negative) fault code
+	  */
+	 int (*read_block)(uint8_t cmd, uint32_t blocksize, uint8_t *buffer);
 
 	/**
 	 * Configures data collection from the Single-wire
@@ -135,5 +141,6 @@ int swd_init_reset(struct command_context *cmd_ctx);
 void swd_add_reset(int req_srst);
 
 bool transport_is_swd(void);
+bool transport_is_cmsis_dap(void);
 
 #endif /* SWD_H */