i2c: designware: Remove needless initializations from i2c_dw_reg_slave()

These struct dw_i2c_dev members are not used in i2c-designware-slave.c
so remove re-initialization of them from i2c_dw_reg_slave().

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