i2c: designware: Remove needless variable from i2c_dw_init_slave()

Commit 43df43e6 ("i2c: designware: Don't set SCL timings and speed
mode when in slave mode") made variable comp_param1 needless in
i2c_dw_init_slave(). Remove it now.

Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Signed-off-by: Jarkko Nikula <jarkko.nikula@linux.intel.com>
Signed-off-by: Wolfram Sang <wsa@the-dreams.de>