ulink_calculate_frequency() is used exclusively when
_DEBUG_JTAG_IO_ is set, no need to compile this
function if it is not used.
Declaring it static in the same commit.
Change-Id: I243ffdf69a1dc3bee6d16e4bb8d78396b6ea5144
Signed-off-by: Alexander Kurz <akurz@blala.de>
Reviewed-on: http://openocd.zylin.com/3241
Tested-by: jenkins
Reviewed-by: Andreas Fritiofson <andreas.fritiofson@gmail.com>