eeprom: at24: fix retrieving the at24_chip_data structure

Commit feb2f19b ("eeprom: at24: move platform data processing into
a separate routine") introduced a bug where we incorrectly retireve the
at24_chip_data structure. Remove the unnecessary ampersand operator.

Fixes: feb2f19b

 ("eeprom: at24: move platform data processing into a separate routine")
Reported-by: Vadim Pasternak <vadimp@mellanox.com>
Signed-off-by: Bartosz Golaszewski <brgl@bgdev.pl>