tpm/st33zp24/spi: Improve st33zp24_spi_evaluate_latency

Add check in st33zp24_spi_evaluate_latency helping to diagnose if the chip
is present or in a bad state.

Signed-off-by: Christophe Ricard <christophe-h.ricard@st.com>
Reviewed-by: Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>
Signed-off-by: Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>

drivers/char/tpm/st33zp24/spi.c

@@ -214,6 +214,11 @@ static int st33zp24_spi_evaluate_latency(void *phy_id)
 						&data, 1);
 		latency++;
 	}
+	if (status < 0)
+		return status;
+	if (latency == MAX_SPI_LATENCY)
+		return -ENODEV;
+
 	return latency - 1;
 } /* evaluate_latency() */