ARC: Do not print JTAG STATUS register each time

It appeared to be a poor decision to print values of JTAG status
register each time after retrieving it, because it is retrieved
constantly in poll() and debug log was floodede with those messages.
This patch removes those annoying messages.

Signed-off-by: Anton Kolesov <anton.kolesov@synopsys.com>
gdb_servser: Fix confusing warning when entering noack mode

Comment in gdb_server code mistakingly attributed constant warnings
about unexpected acknowledgment to the ACK packet sent by GDB when
establishing connection. However that is not the case, OpenOCD
gdb_server is handling this packet correctly without an warnings. This
warning instead was caused by the ACK packet which GDB sends right after
going into noack mode. Because OpenOCD gdb_server is already in noack
mode at this state, it emits warning about it. This is a documented GDB
behavior
(https://sourceware.org/gdb/onlinedocs/gdb/Packet-Acknowledgment.html)
so there is no reason to scare users with warnings in this case.

This patch basically introduces two-level noack mode: after receiving
QStartNoAckMode gdb_server will set noack_mode to 1, then it will
receive this last ACK packet, but instead of printing a warning,
noack_mode will be increased to 2. Should there be any other ACK packets
after that, they will be properly reported by warning. All other code
that relies on noack_mode checks it for "!= 0", so there will be no
difference if it is 1 or 2.

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