sensor_lis2dw: Fix fifo_empty check on lis2dw chips

Fix inverted check for fifo empty.  The fifo is empty when the number
of entries in the fifo is zero.

Signed-off-by: Kevin O'Connor <kevin@koconnor.net>

src/sensor_lis2dw.c

@@ -141,7 +141,7 @@ lis2dw_query(struct lis2dw *ax, uint8_t oid)
         if (ax->model == LIS3DH)
             fifo_empty = fifo[1] & 0x20;
         else
-            fifo_empty = fifo[1] & 0x3F;
+            fifo_empty = ((fifo[1] & 0x3F) == 0);
 
         fifo_ovrn = fifo[1] & 0x40;
 
@@ -167,7 +167,7 @@ lis2dw_query(struct lis2dw *ax, uint8_t oid)
         if (ax->model == LIS3DH)
             fifo_empty = fifo[0] & 0x20;
         else
-            fifo_empty = fifo[0] & 0x3F;
+            fifo_empty = ((fifo[0] & 0x3F) == 0);
 
         fifo_ovrn = fifo[0] & 0x40;