IMU FIFO 샘플 대기 함수 추가

- 샘플 부족 방지 안전장치

src/drivers/imu/imu_i2c.c

@@ -615,6 +615,43 @@ int imu_fifo_start(void)
     return 0;
 }
 
+int imu_fifo_wait_samples(uint16_t target_samples, uint32_t timeout_ms)
+{
+    uint32_t waited_ms = 0U;
+    const uint32_t poll_ms = 10U;
+
+    if (target_samples == 0U)
+    {
+        return 0;
+    }
+
+    if (!fifo_active)
+    {
+        return -EALREADY;
+    }
+
+    while (waited_ms <= timeout_ms)
+    {
+        uint16_t record_count = 0U;
+        int ret = imu_fifo_read_count(&record_count);
+
+        if (ret)
+        {
+            return ret;
+        }
+
+        if (record_count >= target_samples)
+        {
+            return 0;
+        }
+
+        k_msleep(poll_ms);
+        waited_ms += poll_ms;
+    }
+
+    return -ETIMEDOUT;
+}
+
 int imu_fifo_read_latest(uint8_t *sample_bytes,
                          uint16_t max_samples,
                          uint16_t *out_count)