Partial fix to the "long IR length" problems.

 - Current code could handle up to 32 bit IR lengths with
   full functionality, if it didn't just reject may of them
   out of hand.  So only reject clear errors, where the IR
   mask (or capture instruction) needs more than IrLen bits.

 - Longer IR lengths can only be handled in BYPASS mode
   for now.  Example:  TI's DSPs use 38-bit IR lengths.
   So we can't issue their IDCODE instructions...

A more complete fix would be able to issue longer instructions;
or minimally, would fail cleanly for the non-BYPASS case.

Note that this *could* make some currently broken scripts fail,
since the previous code accepted garbage values so long as
they didn't use more than 16 bits.


git-svn-id: svn://svn.berlios.de/openocd/trunk@2222 b42882b7-edfa-0310-969c-e2dbd0fdcd60