platform/chrome: sensorhub: Support devices without FIFO_INT_ENABLE

Some devices (such as Smaug) report having MOTION_SENSE_FIFO but do not
support controlling the behaviour of the FIFO interrupt via the
FIFO_INT_ENABLE command and in these cases the interrupt is always
enabled. However, currently the code assumes that if MOTION_SENSE_FIFO
is supported then so is FIFO_INT_ENABLE, and when it tries to enable
the interrupt via this command and an unsupported device reports a
failure it then propagates this into failing the sensors probe.

Interpret the return value -EINVAL as a device where FIFO_INT_ENABLE is
not present and the interrupt is always enabled.

Signed-off-by: Diogo Ivo <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Tzung-Bi Shih <[e-mail]>

drivers/platform/chrome/cros_ec_sensorhub_ring.c

···
 	/* We expect to receive a payload of 4 bytes, ignore. */
 	if (ret > 0)
 		ret = 0;
+	/*
+	 * Some platforms (such as Smaug) don't support the FIFO_INT_ENABLE
+	 * command and the interrupt is always enabled.  In the case, it
+	 * returns -EINVAL.
+	 *
+	 * N.B: there is no danger of -EINVAL meaning any other invalid
+	 * parameter since fifo_int_enable.enable is a bool and can never
+	 * be in an invalid range.
+	 */
+	else if (ret == -EINVAL)
+		ret = 0;
 
 	return ret;
 }