arc: Add an option to enable paranoia checks for JTAG status RD

Add an option "arc jtag always-check-status-rd on|off" that will force ARC
JTAG layer to check for RD bit of JTAG Status register. See already
existing code that does this before reading from DDR memory. This option is
off by default, since there are no known cases where this check is required
for anything else other than read from DDR memory.

Signed-off-by: Anton Kolesov <Anton.Kolesov@synopsys.com>
arc: [trivial] Formatting of AUX register values in log

Use %08x instead of %x, so that presentation will be same as for core
registers

Signed-off-by: Anton Kolesov <Anton.Kolesov@synopsys.com>
arc: Add a warning when SW breakpoint has been overwritten externally

Signed-off-by: Anton Kolesov <Anton.Kolesov@synopsys.com>
arc: Add JTAG STATUS.FL checks after each operation

Check for FL bit in JTAG STATUS register and return error if this bit is
set, which usually indicates some kind of an error.

This however is disabled by default because it is known to break JTAG: there
is an undesired extra write after the indented one, so if we write, say,
DEBUG AUX register at 0x5, then we will also write same value to PC register
at 0x6, which is totally undesired.

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