dts: arm: stm32: stm32l1x remove eeprom reg attribute & add eeprom sizes

'reg' attribute removed from overall stm32l1 dts,
so eeprom size has to be specified for each SoC
in stm32l1x series.
Adds remaining stm32l1x SoCs that didn't have eeprom size specified yet.
Eeprom size added in stm32l151Xb-a & stm32l151X8-a dtsi files,
(based on device overview in datasheet DocID024330 Rev 5).
Eeprom size added in stm32l151Xb dtsi file (based on
device overview in datasheet DocID17659 Rev 12).

Signed-off-by: Noelle Clement <noelleclement@hotmail.com>