It's been about a year since these were deprecated and, in most
cases, removed.  There's no point in carrying that documentation,
or backwards compatibility for "jtag_device" and "jtag_speed",
around forever.  (Or a few remnants of obsolete code...)

Removed a few obsolete uses of "jtag_speed":

 - The Calao stuff hasn't worked since July 2008.  (Those Atmel
   targets need to work with a 32KHz core clock after reset until
   board-specific init-reset code sets up the PLL and enables a
   faster JTAg clock.)
 - Parport speed controls don't actually work (tops out at about
   1 MHz on typical HW).
 - In general, speed controls need to live in board.cfg files (or
   sometimes target.cfg files), not interface.cfg ...

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