Revert "libpayload: Reset PS/2 keyboard"

Documentation is scarce on the matter, however the related coreboot
code suggests that after the ACK, the keyboard also sends the result
of the self test (passed/failed). It looks like this result is never
consumed here, probably resulting in further confusion for later com-
mands.

Let's revert this for now (if it's not too late for the 4.10 release)
and break things later again. IMHO, due to the fact that there are
dozens of different keyboard controller and keyboard implementations
and no accurate specification followed, such changes should be tested
on a lot of hardware before merge.

This reverts commit a99ed13e33.
This reverts commit 7ae606f57f.

Change-Id: I4d4304d5d8a01e013feac61016c59bcaeea81140
Signed-off-by: Nico Huber <nico.h@gmx.de>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/33244
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Angel Pons <th3fanbus@gmail.com>
Reviewed-by: Martin Kepplinger <martink@posteo.de>
Reviewed-by: Patrick Georgi <pgeorgi@google.com>
Reviewed-by: Felix Held <felix-coreboot@felixheld.de>
Reviewed-by: Furquan Shaikh <furquan@google.com>

payloads/libpayload/drivers/i8042/i8042.h

@@ -63,7 +63,6 @@
 #define I8042_KBCMD_EN			0xf4
 #define I8042_KBCMD_DEFAULT_DIS		0xf5
 #define I8042_KBCMD_SET_DEFAULT		0xf6
-#define I8042_KBCMD_ACK			0xfa
 #define I8042_KBCMD_RESEND		0xfe
 #define I8042_KBCMD_RESET		0xff