boards: arm: b_l072z_lrwan1: Fix incorrect EEPROM documentation
boards: arm: b_l072z_lrwan1: Fix incorrect EEPROM documentation

The documentation page in Zephyr states that the STM32L072CZ has 20KiB
of EEPROM. This is incorrect, the datasheet (and DTS) indicates that
it has 6KiB of EEPROM.

Signed-off-by: Andreas Sandberg <b15c342f1de186996bcca5e1a23cd684d2fadb32@sandberg.pp.se>

finikorg/zephyr,Vudentz/zephyr,zephyrproject-rtos/zephyr,finikorg/zephyr,Vudentz/zephyr,galak/zephyr,finikorg/zephyr,zephyrproject-rtos/zephyr,zephyrproject-rtos/zephyr,galak/zephyr,Vudentz/zephyr,finikorg/zephyr,Vudentz/zephyr,nashif/zephyr,Vudentz/zephyr,galak/zephyr,galak/zephyr,zephyrproject-rtos/zephyr,nashif/zephyr,Vudentz/zephyr,nashif/zephyr,finikorg/zephyr,galak/zephyr,nashif/zephyr,nashif/zephyr,zephyrproject-rtos/zephyr