Remove duplicated initialization

Remove duplicated initialization

I a mail conversation with Øyvind we stated that speed may not be set at
all on case CLOCK_MODE_KHZ and CLOCK_MODE_RCLK. Also there isn't proper
error propagation adapter_khz_to_speed or jtag_rclk_to_speed.
So jtag_get_speed may need some rewrite for error propagation.

CC: Øyvind Harboe <oyvind.harboe@zylin.com>
Signed-off-by: Alexander Stein <alexander.stein@informatik.tu-chemnitz.de>
Signed-off-by: Øyvind Harboe <oyvind.harboe@zylin.com>