i2c: core: Drop duplicate check before calling OF APIs

i2c: core: Drop duplicate check before calling OF APIs

OF APIs are usually NULL-aware and return an error in case when
device node is not present or supported. We already have a check
for the returned value, no need to check for the parameter.

Tested-by: Tomi Valkeinen <tomi.valkeinen@ideasonboard.com>
Reviewed-by: Sakari Ailus <sakari.ailus@linux.intel.com>
Acked-by: Sakari Ailus <sakari.ailus@linux.intel.com>
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Signed-off-by: Wolfram Sang <wsa+renesas@sang-engineering.com>