doc: remove reference to already dropped tftp support

The only code dealing with tftp in OpenOCD was in eCos build, code
already dropped in commit 39650e2273 ("ecosboard: delete
bit-rotted eCos code") almost 8 years ago.

Drop tftp related documentation too.

Change-Id: I0defc8f844e74c90894dca04a652dcc497a520e1
Signed-off-by: Antonio Borneo <borneo.antonio@gmail.com>
Reviewed-on: http://openocd.zylin.com/5913
Tested-by: jenkins
Reviewed-by: Jonathan McDowell <noodles-openocd@earth.li>

doc/openocd.texi

@@ -79,7 +79,6 @@ Free Documentation License''.
 * JTAG Commands::                    JTAG Commands
 * Boundary Scan Commands::           Boundary Scan Commands
 * Utility Commands::                 Utility Commands
-* TFTP::                             TFTP
 * GDB and OpenOCD::                  Using GDB and OpenOCD
 * Tcl Scripting API::                Tcl Scripting API
 * FAQ::                              Frequently Asked Questions
@@ -10371,28 +10370,6 @@ For quickstart instructions run:
 openocd -f tools/firmware-recovery.tcl -c firmware_help
 @end example
 
-@node TFTP
-@chapter TFTP
-@cindex TFTP
-If OpenOCD runs on an embedded host (as ZY1000 does), then TFTP can
-be used to access files on PCs (either the developer's PC or some other PC).
-
-The way this works on the ZY1000 is to prefix a filename by
-"/tftp/ip/" and append the TFTP path on the TFTP
-server (tftpd). For example,
-
-@example
-load_image /tftp/10.0.0.96/c:\temp\abc.elf
-@end example
-
-will load c:\temp\abc.elf from the developer pc (10.0.0.96) into memory as
-if the file was hosted on the embedded host.
-
-In order to achieve decent performance, you must choose a TFTP server
-that supports a packet size bigger than the default packet size (512 bytes). There
-are numerous TFTP servers out there (free and commercial) and you will have to do
-a bit of googling to find something that fits your requirements.
-
 @node GDB and OpenOCD
 @chapter GDB and OpenOCD
 @cindex GDB