tcl/interface/ftdi: Add imx8mp-evk internal JTAG interface

tcl/interface/ftdi: Add imx8mp-evk internal JTAG interface

The imx8mp-evk board has a FT4232H chip connected to the chip's JTAG
pins.

Switching between this on-board interface and the external ARM-10
connector is controlled by an GPIO which is behind an i2c expander
connected to the same FTDI chip.

Switching can be performed using the NXP bcu tool:

	https://github.com/NXPmicro/bcu

Change-Id: Ic910515f76eaf09ea6d0f755b026fb09cf09ccfc
Signed-off-by: Leonard Crestez <leonard.crestez@nxp.com>
Reviewed-on: http://openocd.zylin.com/5426
Tested-by: jenkins
Reviewed-by: Tomas Vanek <vanekt@fbl.cz>