cpu/stm32l1: add definitions for internal eeprom

cpu/stm32l1/Makefile.features

 FEATURES_PROVIDED += periph_flash_common
 FEATURES_PROVIDED += periph_flashpage
 FEATURES_PROVIDED += periph_flashpage_raw
+FEATURES_PROVIDED += periph_eeprom
 
 -include $(RIOTCPU)/stm32_common/Makefile.features

cpu/stm32l1/include/cpu_conf.h

@@ -93,6 +93,18 @@ extern "C" {
 #define FLASHPAGE_RAW_ALIGNMENT    (4U)
 /** @} */
 
+/**
+ * @name    EEPROM configuration
+ * @{
+ */
+#define EEPROM_START_ADDR          (0x08080000)
+#if defined(CPU_MODEL_STM32L152RE)
+#define EEPROM_SIZE                (16384UL)  /* 16kB */
+#elif defined(CPU_MODEL_STM32L151RC)
+#define EEPROM_SIZE                (8192U)    /* 8kB */
+#endif
+/** @} */
+
 #ifdef __cplusplus
 }
 #endif