m68k/mac: Don't hang waiting for Cuda power-down command

Testing shows that the CUDA_POWERDOWN command never completes (for a
Centris 660av or LC 475, at least). So, don't wait for command completion
on those Cuda-based models that do not support soft power. Just proceed to
log the usual message, "It is now safe to turn off your Macintosh."
Reported-by: NStan Johnson <userm57@yahoo.com>
Tested-by: NStan Johnson <userm57@yahoo.com>
Signed-off-by: NFinn Thain <fthain@telegraphics.com.au>
Signed-off-by: NGeert Uytterhoeven <geert@linux-m68k.org>

arch/m68k/mac/misc.c

@@ -357,6 +357,17 @@ static void cuda_shutdown(void)
 	struct adb_request req;
 	if (cuda_request(&req, NULL, 2, CUDA_PACKET, CUDA_POWERDOWN) < 0)
 		return;
+
+	/* Avoid infinite polling loop when PSU is not under Cuda control */
+	switch (macintosh_config->ident) {
+	case MAC_MODEL_C660:
+	case MAC_MODEL_Q605:
+	case MAC_MODEL_Q605_ACC:
+	case MAC_MODEL_P475:
+	case MAC_MODEL_P475F:
+		return;
+	}
+
 	while (!req.complete)
 		cuda_poll();
 }