Add support for FT232H chips

Add support for FT232H chips

FT232H chips are new highspeed devices from FTDI. Basically these are a half of FT2232H (or a quarter of FT4232H), so only one channel which can be used as OpenOCD
interface. The chips are supported by libftdi 0.20 or later and by ftd2xx 2.08.12 or later.

Change-Id: Ic9a2c279167c3419a24f0d6befacbb83c4ffeb25
Signed-off-by: Freddie Chopin <freddie.chopin@gmail.com>
Reviewed-on: http://openocd.zylin.com/736
Tested-by: jenkins
Reviewed-by: Spencer Oliver <spen@spen-soft.co.uk>
Reviewed-by: Salvador Arroyo <sarroyofdez@yahoo.es>