i2c: bcm-iproc: Use complete() instead of complete_all()

There is only one waiter for the completion, therefore there
is no need to use complete_all(). Let's make that clear by
using complete() instead of complete_all().

The usage pattern of the completion is:

bcm_iproc_i2c_xfer_single_msg()
  reinit_completion()
  ...
  (activate the transfer)
  ...
  wait_for_completion_timeout()

Signed-off-by: Daniel Wagner <daniel.wagner@bmw-carit.de>
Acked-by: Ray Jui <ray.jui@broadcom.com>
Signed-off-by: Wolfram Sang <wsa@the-dreams.de>