Add support for the GOEPEL PicoTAP programmer

http://www.goepel.com/en/jtagboundary-scan/hardware/picotap.html

This device is actually a JTAG adapter, but since it uses standard
FT2232 A interface pins, it can be easily used as SPI programmer
(tested it here successfully). PicoTAP supports only 5V output, so one
needs to reduce this to 3.3V in a same manner as DLP Design DLP-USB1232H, see

  http://flashrom.org/FT2232SPI_Programmer#DLP_Design_DLP-USB1232H

for details.

The PicoTAP pin-out is as follows:

  PicoTAP |  SPI
 ---------+-------
    TCK   | SCLK
    TMS   |  CS#
    TDI   |  SO
    TDO   |  SI
   /TRST  |  -
    GND   |  GND
    +5V   |  VCC, HOLD# & WP# after 3.3V regulator

I managed to run PicoTAP in 10MHz, 15MHz and 30MHz modes (by forcing
DIVIDE_BY), against SST25VF016B SPI flash, read/write/erase all worked
fine (write seems somewhat slow).

Corresponding to flashrom svn r1453.

Signed-off-by: Samir Ibradžić <sibradzic@gmail.com>
Acked-by: Uwe Hermann <uwe@hermann-uwe.de>
diff --git a/flashrom.8 b/flashrom.8
index 7a012de..a8f4660 100644
--- a/flashrom.8
+++ b/flashrom.8
@@ -199,8 +199,8 @@
 based USB SPI programmer), including the DLP Design DLP-USB1232H, \
 FTDI FT2232H Mini-Module, FTDI FT4232H Mini-Module, openbiosprog-spi, Amontec \
 JTAGkey/JTAGkey-tiny/JTAGkey-2, Dangerous Prototypes Bus Blaster, \
-Olimex ARM-USB-TINY/-H, Olimex ARM-USB-OCD/-H, and TIAO/DIYGADGET USB
-Multi-Protocol Adapter (TUMPA).
+Olimex ARM-USB-TINY/-H, Olimex ARM-USB-OCD/-H, TIAO/DIYGADGET USB
+Multi-Protocol Adapter (TUMPA), and GOEPEL PicoTAP.
 .sp
 .BR "* serprog" " (for flash ROMs attached to a programmer speaking serprog), \
 including AVR flasher by Urja Rannikko, AVR flasher by eightdot, \
@@ -443,7 +443,7 @@
 can be
 .BR 2232H ", " 4232H ", " jtagkey ", " busblaster ", " openmoko ", " \
 arm-usb-tiny ", " arm-usb-tiny-h ", " arm-usb-ocd ", " arm-usb-ocd-h \
-", or " tumpa
+", " tumpa ", or " picotap
 and
 .B interface
 can be