configure.ac: fix build with libusb0 and without libusb1

configure.ac: fix build with libusb0 and without libusb1

Driver 'openjtag' requires both libftdi and libusb1.
The current check is incorrect and the driver is built when
libftdi is present with libusb0 and without libusb1, which causes
the linker to fail resolving the required libusb1 symbols.

Remove the check for libusb0 on driver 'openjtag'.
Create a new adapters group LIBFTDI_USB1_ADAPTERS to hold the
driver 'openjtag'.

Change-Id: I1f5e554b519e51c829d116ede894639cb55a26aa
Signed-off-by: Antonio Borneo <borneo.antonio@gmail.com>
Reviewed-on: http://openocd.zylin.com/5989
Tested-by: jenkins