ARC: Remove JTAG test function

This is a custom function that seems to be redundant nowdays as it
doesn't server any purpose from user-perspective.

Signed-off-by: Anton Kolesov <anton.kolesov@synopsys.com>
ARC: Refactor setting JTAG instruction

Rename arc_jtag_v2_set_instruction to arc_jtag_v2_set_ir. Always set
endstate to TAP_IRPAUSE.

Signed-off-by: Anton Kolesov <anton.kolesov@synopsys.com>
ARC: Refactor idcode_read function

Use new JTAG API instead of an old one.

Signed-off-by: Anton Kolesov <anton.kolesov@synopsys.com>
ARC: Update arc_jtag_read_status function

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

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