i2c: designware: Uninline i2c_dw_probe()

Since i2c_dw_probe() is going to be extended, uninline it to reduce
the noise in the common header.

Reviewed-by: Andi Shyti <andi.shyti@kernel.org>
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Acked-by: Jarkko Nikula <jarkko.nikula@linux.intel.com>
Tested-by: Serge Semin <fancer.lancer@gmail.com>
Signed-off-by: Andi Shyti <andi.shyti@kernel.org>