#39 t500: Add T9400 as supported cpu and add missing flashing instructions

bridging pin 1 and 9, as directed by the added instructions, would mean bringing wp and hold (for soic-16 25xx flash) on the board in question, these pins are already held high via separate pull-up resistors, enabling the flash operation. this is why excluding the wp/hold wires when wiring the clip is advised. further, the change is unrelated to the other change, regarding cpu compatibility split these up and submit only the cpu info. the information about wp/hold is at best, superfluous (i don't see what good it would do) the wp/hold instructions in the diff also say to do that "if read and write don't work" - usually that is a bad clip, bad wiring, or too long wires i'm closing this pull request, in its current state.