leds: hw acceleration for Clevo mail LED driver

Add support for hardware accelerated LED blinking for the mail LED
commonly found on Clevo notebooks.

Signed-off-by: Márton Németh <nm127@freemail.hu>
Signed-off-by: Richard Purdie <rpurdie@rpsys.net>
diff --git a/drivers/leds/Kconfig b/drivers/leds/Kconfig
index 659448e..922c3df 100644
--- a/drivers/leds/Kconfig
+++ b/drivers/leds/Kconfig
@@ -122,9 +122,11 @@
 	  programs through the leds subsystem. This LED have three
 	  known mode: off, blink at 0.5Hz and blink at 1Hz.
 
-	  As this LED cannot change it's brightness it blinks instead.
-	  The brightness value 0 means off, 1..127 means blink at 0.5Hz
-	  and 128..255 means blink at 1Hz.
+	  The driver supports two kinds of interface: using ledtrig-timer
+	  or through /sys/class/leds/clevo::mail/brightness. As this LED
+	  cannot change it's brightness it blinks instead. The brightness
+	  value 0 means off, 1..127 means blink at 0.5Hz and 128..255 means
+	  blink at 1Hz.
 
 	  This module can drive the mail LED for the following notebooks: