platform/x86: acer-wmi: Silence "unsupported" message a bit

This driver prints that "Unsupported machine..." message on every boot on
ThinkPad X1 Carbon laptops (and I assume a number of other systems), which
causes graphical boots to "glitch" a bit and is rather annoying ...

Make it a pr_debug instead.
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>

drivers/platform/x86/acer-wmi.c

@@ -2213,7 +2213,7 @@ static int __init acer_wmi_init(void)
 	if (wmi_has_guid(AMW0_GUID1) &&
 	    !dmi_check_system(amw0_whitelist) &&
 	    quirks == &quirk_unknown) {
-		pr_err("Unsupported machine has AMW0_GUID1, unable to load\n");
+		pr_debug("Unsupported machine has AMW0_GUID1, unable to load\n");
 		return -ENODEV;
 	}