soc/intel/ehl: Replace dt HeciEnabled by HECI1 disable config

The only option to make HECI1 function disable on Elkhart Lake SoC
platform is using SBI under SMM mode.

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.

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: I76c625e6221fdef1343599e7dbc7739caa91bf98
Reviewed-on: https://review.coreboot.org/c/coreboot/+/60727
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Sheng Lean Tan <sheng.tan@9elements.com>

src/soc/intel/elkhartlake/smihandler.c

@@ -16,11 +16,7 @@
  */
 void smihandler_soc_at_finalize(void)
 {
-	const struct soc_intel_elkhartlake_config *config;
-
-	config = config_of_soc();
-
-	if (!config->HeciEnabled && CONFIG(HECI_DISABLE_USING_SMM))
+	if (CONFIG(DISABLE_HECI1_AT_PRE_BOOT))
 		heci_disable();
 }