Added board config for nuttx sim.

src/drivers/boards/sim/board_config.h

+#define UDID_START		0x1FFF7A10
+
+/*
+ * I2C busses
+ */
+#define PX4_I2C_BUS_ESC		1
+#define PX4_SIM_BUS_TEST	2
+#define PX4_I2C_BUS_EXPANSION	3
+#define PX4_I2C_BUS_LED		3
+
+#define PX4_I2C_OBDEV_LED	0x55
+
+#define STM32_SYSMEM_UID "SIMULATIONID"