eeprom: at24: remove at24_platform_data from at24_data

Not all fields from at24_platform_data are needed in at24_data. Let's
keep just the ones we need and not carry the whole platform_data
structure all the time.

Signed-off-by: Bartosz Golaszewski <brgl@bgdev.pl>
Tested-by: Andy Shevchenko <andy.shevchenko@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>