add board/redbee-econotag.cfg and JTAG support

add board/redbee-econotag.cfg and JTAG support

The Redbee Econotag is an open hardware development kit from
Redwire, LLC (www.redwirellc.com/store), for the Freescale
MC13224V ARM7TDMI + 802.15.4 radio.

It includes both an MC13224V and an FT2232H (for JTAG and UART
support).  It has flexible power supply options.

Additional features are:

  - inverted-F pcb antenna
  - 36 GPIO brought out to 0.1" pin header
    (includes all peripheral pins)
  - Reset button
  - Two push buttons (on kbi1-5 and kbi0-4)
  - USB-A connector, powered from USB
  - up to 16V external input
  - pads for optional buck inductor
  - pads for optional 32.768kHz crystal
  - 2x LEDS on TX_ON and RX_ON

[ dbrownell@users.sourceforge.net: shrink lines; texi ]

Signed-off-by: David Brownell <dbrownell@users.sourceforge.net>