nrf51: Fix format string bugs in nrf51_info

Additional information string appended to the 'flash info' output used
incorrect offsets and was missing a couple of fields.

Signed-off-by: Andrey Smirnov <andrew.smirnov@gmail.com>
Change-Id: If131be021295cab6adfca7da03c2f0fb8dca7d42
Reviewed-on: http://openocd.zylin.com/2011
Tested-by: jenkins
Reviewed-by: Spencer Oliver <spen@spen-soft.co.uk>
stlink: Use callback to increase frequency of trace data sampling

The ST-LINK/V2 has limited internal buffering, such that trace data
can be missed if the target is generating data at a rate quicker than
the OpenOCD trace sampling. The issue of lost data is compounded since
individual TPIU packets may be split across individual STLINK_TRACE_EP
reads, and misleading results can occur if mid-packet loss occurs.

This patch increases the frequency of checking for pending trace data
with the aim of minimising such losses. Note: With the limited (I/O
and memory) bandwidth of the ST-LINK/V2 there cannot, however, be a
guarantee against trace data loss.

The timer callback is only added when enabling tracing, and is removed
when tracing is disabled.

Change-Id: Ibde9794b77793d3068f88cb5c1a26f9ceadcbd8a
Signed-off-by: James G. Smith <jsmith@ecoscentric.com>
Signed-off-by: Andreas Fritiofson <andreas.fritiofson@gmail.com>
Reviewed-on: http://openocd.zylin.com/1661
Tested-by: jenkins