arch: arm: stm32l4: add missing I2C_3 to dts.fixup

One can enable I2C_3 in kconfig and set status = "ok" in dts, but
the driver expects to find the config as fixed up with this
addition.

Signed-off-by: Kiril Zyapkov <k.zyapkov@allterco.com>

arch/arm/soc/st_stm32/stm32l4/dts.fixup

@@ -54,6 +54,14 @@
 #define CONFIG_I2C_2_ERROR_IRQ                  ST_STM32_I2C_V2_40005800_IRQ_ERROR
 #define CONFIG_I2C_2_BITRATE                    ST_STM32_I2C_V2_40005800_CLOCK_FREQUENCY
 
+#define CONFIG_I2C_3_BASE_ADDRESS               ST_STM32_I2C_V2_40005C00_BASE_ADDRESS
+#define CONFIG_I2C_3_EVENT_IRQ_PRI              ST_STM32_I2C_V2_40005C00_IRQ_EVENT_PRIORITY
+#define CONFIG_I2C_3_ERROR_IRQ_PRI              ST_STM32_I2C_V2_40005C00_IRQ_ERROR_PRIORITY
+#define CONFIG_I2C_3_NAME                       ST_STM32_I2C_V2_40005C00_LABEL
+#define CONFIG_I2C_3_EVENT_IRQ                  ST_STM32_I2C_V2_40005C00_IRQ_EVENT
+#define CONFIG_I2C_3_ERROR_IRQ                  ST_STM32_I2C_V2_40005C00_IRQ_ERROR
+#define CONFIG_I2C_3_BITRATE                    ST_STM32_I2C_V2_40005C00_CLOCK_FREQUENCY
+
 #define CONFIG_I2C_4_BASE_ADDRESS               ST_STM32_I2C_V2_40008400_BASE_ADDRESS
 #define CONFIG_I2C_4_EVENT_IRQ_PRI              ST_STM32_I2C_V2_40008400_IRQ_EVENT_PRIORITY
 #define CONFIG_I2C_4_ERROR_IRQ_PRI              ST_STM32_I2C_V2_40008400_IRQ_ERROR_PRIORITY