jtag: remove file driver.h

jtag: remove file driver.h

The only purpose of include file driver.h was to expose the API
to register the adapter's commands.

Move the prototype in adapter.h, already used by openocd.c.

Change-Id: Ie1090c60ef9e5bac5ea187c87bed6e7b08d9671c
Signed-off-by: Antonio Borneo <borneo.antonio@gmail.com>
Reviewed-on: https://review.openocd.org/c/openocd/+/6645
Tested-by: jenkins
Reviewed-by: Tarek BOCHKATI <tarek.bouchkati@gmail.com>