skylake: Remove "IshEnable"

Remove "IshEnable" from soc_intel_skylake_config since it's not
used anymore.

Enable/disable ISH by checking if ISH device is turned on or not.

Refer to https://review.coreboot.org/#/c/coreboot/+/26485/.

BUG=b:79244403
BRANCH=none
TEST=Built.

Change-Id: I4d2889af118659852431c87cb516fd19b577efc5
Signed-off-by: li feng <li1.feng@intel.com>
Reviewed-on: https://review.coreboot.org/26521
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Furquan Shaikh <furquan@google.com>

src/soc/intel/skylake/chip.h

@@ -287,9 +287,6 @@ struct soc_intel_skylake_config {
 	u8 ScsEmmcHs400Enabled;
 	u8 ScsSdCardEnabled;
 
-	/* Integrated Sensor */
-	u8 IshEnable;
-
 	u8 PttSwitch;
 	u8 HeciTimeouts;
 	u8 HsioMessaging;