Input: i8042 - reset keyboard to fix Elantech touchpad detection

On some laptops, keyboard needs to be reset in order to successfully detect
touchpad (e.g., some Gigabyte laptop models with Elantech touchpads).
Without resettin keyboard touchpad pretends to be completely dead.

Based on the original patch by Mateusz Jończyk this version has been
expanded to include DMI based detection & application of the fix
automatically on the affected models of laptops. This has been confirmed to
fix problem by three users already on three different models of laptops.

Bugzilla: https://bugzilla.kernel.org/show_bug.cgi?id=81331
Cc: stable@vger.kernel.org
Signed-off-by: Srihari Vijayaraghavan <linux.bug.reporting@gmail.com>
Acked-by: Mateusz Jończyk <mat.jonczyk@o2.pl>
Tested-by: Srihari Vijayaraghavan <linux.bug.reporting@gmail.com>
Tested by: Zakariya Dehlawi <zdehlawi@gmail.com>
Tested-by: Guillaum Bouchard <guillaum.bouchard@gmail.com>
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>
diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt
index 10d51c2..8013b4d 100644
--- a/Documentation/kernel-parameters.txt
+++ b/Documentation/kernel-parameters.txt
@@ -1243,6 +1243,7 @@
 	i8042.notimeout	[HW] Ignore timeout condition signalled by controller
 	i8042.reset	[HW] Reset the controller during init and cleanup
 	i8042.unlock	[HW] Unlock (ignore) the keylock
+	i8042.kbdreset  [HW] Reset device connected to KBD port
 
 	i810=		[HW,DRM]