ARC: Unify JTAG API

Signed-off-by: Anton Kolesov <anton.kolesov@synopsys.com>
ARC: Remove old code

Signed-off-by: Anton Kolesov <anton.kolesov@synopsys.com>
ARC: Polishing internal

Signed-off-by: Anton Kolesov <anton.kolesov@synopsys.com>
ARC: Streamline internal JTAG functions

Signed-off-by: Anton Kolesov <anton.kolesov@synopsys.com>
ARC: Combine write_ir and write_transaction

Because writing transaction register is always preceded by writing
instruction register it is convenient to call write_ir from
write_transaction. write_transaction is also getting renamed to
set_transaction, to signify that now it is not just a write to one
specific register.

Signed-off-by: Anton Kolesov <anton.kolesov@synopsys.com>
ARC: Rename transaction reset function

Signed-off-by: Anton Kolesov <anton.kolesov@synopsys.com>
ARC: More refactoring

Signed-off-by: Anton Kolesov <anton.kolesov@synopsys.com>
ARC: Improve documentation

Signed-off-by: Anton Kolesov <anton.kolesov@synopsys.com>
ARC: Rename function to be consistent with generic ones

Signed-off-by: Anton Kolesov <anton.kolesov@synopsys.com>