Revert "Input: i8042 - disable active multiplexing by default"

This reverts commit 68da166491655bc54051bf04c78ce648e2e33508.

It turns out that the assertion about scope of regressions due to
always keeping keyboard controller in legacy mode was proven wrong.
There are laptops, such as Clevo W650SH, that only have internal
touchpad (no external PS/2 ports), that require active multiplexing
mode to switch the touchpad (Elantech) into native mode instead of
basic PS/2 emulation.

Reported-by: Roel Aaij <roel.aaij@gmail.com>
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>
diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt
index 6b10543..10d51c2 100644
--- a/Documentation/kernel-parameters.txt
+++ b/Documentation/kernel-parameters.txt
@@ -1237,7 +1237,7 @@
 	i8042.noloop	[HW] Disable the AUX Loopback command while probing
 			     for the AUX port
 	i8042.nomux	[HW] Don't check presence of an active multiplexing
-			     controller. Default: true.
+			     controller
 	i8042.nopnp	[HW] Don't use ACPIPnP / PnPBIOS to discover KBD/AUX
 			     controllers
 	i8042.notimeout	[HW] Ignore timeout condition signalled by controller