soc/intel/skl: Replace dt `HeciEnabled` by `HECI1 disable` config

List of changes:

1. Drop `HeciEnabled` from dt and dt chip configuration.
2. Replace all logic that disables HECI1 based on the `HeciEnabled`
chip config with `DISABLE_HECI1_AT_PRE_BOOT` config.
3. Make dt CSE PCI device `on` by default.
4. Mainboards set DISABLE_HECI1_AT_PRE_BOOT=y to make Heci1
function disable at pre-boot instead of the dt policy that uses
`HeciEnabled = 0`.

Mainboards that choose to make HECI1 enable during boot don't override
`heci1 disable` config.

Signed-off-by: Subrata Banik <subratabanik@google.com>
Change-Id: I5c13fe4a78be44403a81c28b1676aecc26c58607
Reviewed-on: https://review.coreboot.org/c/coreboot/+/60722
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Tim Wawrzynczak <twawrzynczak@chromium.org>
diff --git a/src/mainboard/clevo/kbl-u/variants/n13xwu/devicetree.cb b/src/mainboard/clevo/kbl-u/variants/n13xwu/devicetree.cb
index db4d1ac..d22f574 100644
--- a/src/mainboard/clevo/kbl-u/variants/n13xwu/devicetree.cb
+++ b/src/mainboard/clevo/kbl-u/variants/n13xwu/devicetree.cb
@@ -60,9 +60,7 @@
 			register "usb3_ports[3]" = "USB3_PORT_DEFAULT(OC_SKIP)"	# Type-A, left
 		end
 		device ref thermal	on	end
-		device ref heci1	on
-			register "HeciEnabled" = "1"
-		end
+		device ref heci1	on	end
 		device ref sata		on
 			register "SataSalpSupport" = "0"
 			# Ports