sharpend JTAG docs w.r.t. hw fifo implementations and retired...

sharpend JTAG docs w.r.t. hw fifo implementations and retired jtag_cancel_queue() which is inheritely incompatible with a hw fifo concept.

git-svn-id: svn://svn.berlios.de/openocd/trunk@328 b42882b7-edfa-0310-969c-e2dbd0fdcd60