stlink: default dapdirect to SWD instead of JTAG

stlink: default dapdirect to SWD instead of JTAG

When the transport is not specified, OpenOCD uses the first listed
by the selected adapter driver.
The old HLA driver for stlink lists SWD as first. The new driver
dapdirect instead lists JTAG, making more difficult a fallback to
HLA when dapdirect is not available due to old stlink FW.
Plus, in case of JTAG wiring, SWD is still possible, while the
opposite is not.

Reorder the list of transports to grant the default to SWD.

Change-Id: Id9c529e921b148d5b352d4603a9028c2a5f15d83
Signed-off-by: Antonio Borneo <borneo.antonio@gmail.com>
Suggested-by: Tarek BOCHKATI <tarek.bouchkati@gmail.com>
Reviewed-on: http://openocd.zylin.com/5538
Tested-by: jenkins
Reviewed-by: Tarek BOCHKATI <tarek.bouchkati@gmail.com>