adapter: switch from struct jtag_interface to adapter_driver

adapter: switch from struct jtag_interface to adapter_driver

To reorganize the adapters code, introduce an adapter_driver
struct that contains all the adapter generic part, while
keeping in two separate struct the specific API jtag_ops and
swd_ops.
Move the allocation of *adapter_driver from the JTAG-specific
file core.c to the more adapter-specific file adapter.c
While splitting the old jtag_interface for every driver, put
the fields in the same order as in the struct declaration so
we keep a consistent code across all the drivers.

While other transport specific API could/would be added as
separate ops, nothing is done here for HLA.

Change-Id: I2d60f97ac514c0dd2d93a6ec9be66fd9d388dad5
Signed-off-by: Antonio Borneo <borneo.antonio@gmail.com>
Reviewed-on: http://openocd.zylin.com/4900
Tested-by: jenkins
Reviewed-by: Tomas Vanek <vanekt@fbl.cz>