thinkpad-acpi: Add mute and mic-mute LED functionality

The LEDs are currently not visible to userspace, for security
reasons. They are exported through thinkpad_acpi.h for use by the
snd-hda-intel driver.

Thanks to Alex Hung <alex.hung@canonical.com> and Takashi Iwai
<tiwai@suse.de> for writing parts of this patch.

Signed-off-by: David Henningsson <david.henningsson@canonical.com>
Acked-by: Henrique de Moraes Holschuh <hmh@hmh.eng.br>
Signed-off-by: Takashi Iwai <tiwai@suse.de>

include/linux/thinkpad_acpi.h

@@ -0,0 +1,15 @@
+#ifndef __THINKPAD_ACPI_H__
+#define __THINKPAD_ACPI_H__
+
+/* These two functions return 0 if success, or negative error code
+   (e g -ENODEV if no led present) */
+
+enum {
+	TPACPI_LED_MUTE,
+	TPACPI_LED_MICMUTE,
+	TPACPI_LED_MAX,
+};
+
+int tpacpi_led_set(int whichled, bool on);
+
+#endif