Integrate asynchronous GPS IMU fusion

soc/software/gps_system/header/imu/imu_sample.h

@@ -0,0 +1,18 @@
+#ifndef IMU_SAMPLE_H
+#define IMU_SAMPLE_H
+
+#include <stdint.h>
+
+/*
+ * Sensor-independent, calibrated inertial sample in SI units.  Drivers and
+ * IMU management publish this type without depending on GPS or ESKF headers.
+ */
+typedef struct {
+	uint64_t timestamp_ticks;
+	double accel_mps2[3];
+	double gyro_rps[3];
+	double temperature_c;
+	uint32_t sequence;
+} imu_sample_t;
+
+#endif