mainboard/google/reef: Remove tablet mode switch support

The _SB.DPTF.TPET ACPI code attached to EC_ENABLE_TABLET_EVENT doesn't
exist in the apollo lake code.  Remove it from reef as part of the
cleanup to update to the new version of IASL.

This was in commit 4f803ac28f (mainboards/google/reef: Add support for
tablet mode switch.)

Change-Id: Ic10c418ddc708c1aed87ad4a9861f04d32445116
Signed-off-by: Martin Roth <martinroth@google.com>
Reviewed-on: https://review.coreboot.org/25982
Reviewed-by: Aaron Durbin <adurbin@chromium.org>
Reviewed-by: Duncan Laurie <dlaurie@chromium.org>
Reviewed-by: Furquan Shaikh <furquan@google.com>
Reviewed-by: Sumeet R Pawnikar <sumeet.r.pawnikar@intel.com>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>

src/mainboard/google/reef/variants/baseboard/include/baseboard/ec.h

@@ -71,9 +71,6 @@
 #define EC_ENABLE_LID_SWITCH
 #define EC_ENABLE_WAKE_PIN	GPE_EC_WAKE
 
-/* Enable Tablet switch */
-#define EC_ENABLE_TABLET_EVENT
-
 #define EC_ENABLE_TBMC_DEVICE
 
 #define SIO_EC_MEMMAP_ENABLE     /* EC Memory Map Resources */