intel/skylake: Disable FADT.8042 if NO_FADT_8042 is set

Kernel relies on FADT 8042 flag to enable/disable
8042 interface. If FADT reports 8042 capability and
8042 (/PS2) capability is actually disabled by coreboot,
kernel would assume the presence of 8042 based on the
FADT flag. This results in undesired system power off when
kernel tries to access the 8042 memory region. To address
this, CONFIG_NO_FADT_8042 was added to selectively
disable 8042 on FADT.

BUG=chrome-os-partner:61858
TEST=Boot OS and verify FADT 8042 flag

Change-Id: Ic80b3835cb5cccdde1203e24a58e28746b0196fc
Signed-off-by: Jenny TC <jenny.tc@intel.com>
Reviewed-on: https://review.coreboot.org/18307
Tested-by: build bot (Jenkins)
Reviewed-by: Furquan Shaikh <furquan@google.com>
diff --git a/src/soc/intel/skylake/Kconfig b/src/soc/intel/skylake/Kconfig
index 24c2e30..090fa2a 100644
--- a/src/soc/intel/skylake/Kconfig
+++ b/src/soc/intel/skylake/Kconfig
@@ -242,4 +242,10 @@
 	default 24 if PLATFORM_USES_FSP2_0
 	default 20 if PLATFORM_USES_FSP1_1
 
+config NO_FADT_8042
+	bool
+	default n
+	help
+	  Choose this option if you want to disable 8042 Keyboard
+
 endif