misc: at25: Factor out at_fram_to_chip()

In the similar way as it's done for EEPROM, factor out
a new helper function for FRAM.

Acked-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Link: https://lore.kernel.org/r/20211125213203.86693-8-andriy.shevchenko@linux.intel.com


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>