If a bus busy is detected when intializing the driver,
toggle 9 times the scl pin. Therefore enable the test mode
of the controller, in which the scl, sda pins can be
controlled manually.

Tested on the siemens boards pxm2, rut and dxr2.

Signed-off-by: Heiko Schocher <hs@denx.de>
Cc: Tom Rini <trini@ti.com>
Cc: Hannes Petermaier <oe5hpm@oevsv.at>
Cc: Lubomir Popov <lpopov@mm-sol.com>
Cc: Steve Sakoman <steve@sakoman.com>
Cc: Sandeep Paulraj <s-paulraj@ti.com>
Cc: Vincent Stehlé <v-stehle@ti.com>
Cc: Samuel Egli <samuel.egli@siemens.com>