l3gd20: disable the FIFO

the FIFO was not gaining us anything, and was adding latency. If we
use the FIFO we'd need to do multiple SPI transfers to ensure it is
drained

src/drivers/l3gd20/l3gd20.cpp

@@ -342,7 +342,11 @@ L3GD20::init()
 	write_reg(ADDR_CTRL_REG5, 0);
 
 	write_reg(ADDR_CTRL_REG5, REG5_FIFO_ENABLE);		/* disable wake-on-interrupt */
-	write_reg(ADDR_FIFO_CTRL_REG, FIFO_CTRL_STREAM_MODE);	/* Enable FIFO, old data is overwritten */
+
+        /* disable FIFO. This makes things simpler and ensures we
+         * aren't getting stale data. It means we must run the hrt
+         * callback fast enough to not miss data. */
+	write_reg(ADDR_FIFO_CTRL_REG, FIFO_CTRL_BYPASS_MODE);	
 
 	set_range(2000);			/* default to 2000dps */
 	set_samplerate(0);			/* max sample rate */