src/jtag/drivers/ftdi: fix swd pin comment and links

src/jtag/drivers/ftdi: fix swd pin comment and links

- TDI/DO is not pin 2 and in fact, we don't even need to mention which
pin number it is. "TDI/DO pin" is descriptive enough.

- FT2232D link didn't work anymore. It could have been updated to the
current working FT2232D link but changed to link the FT2232H instead
which is the latest generation and the most commonly used these days.

- Taking advantage of the change, link to the MPSSE document updated.
It still worked but through a redirection, so updated just in case the
redirection stops working.

Change-Id: Ia7d01bbcac2158026831edb010a6b50f58351e42
Signed-off-by: Diego Herranz <diegoherranz@diegoherranz.com>
Reviewed-on: http://openocd.zylin.com/4908
Tested-by: jenkins
Reviewed-by: Andreas Fritiofson <andreas.fritiofson@gmail.com>