mb/facebook/monolith: Drop PWRB device

The mainboard ASL code contained a power button definition. This is not
required as the system uses the standard ACPI power button.

Remove the PWRB device from ASL.

BUG=N/A
TEST=tested using fwts on a facebook monolith.

Found-by: fwts 19.12.00
Change-Id: I25a842539ee2e8febc8a1ae88843a71ccb4ee68e
Signed-off-by: Wim Vervoorn <wvervoorn@eltan.com>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/38133
Reviewed-by: Frans Hendriks <fhendriks@eltan.com>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>

src/mainboard/facebook/monolith/acpi/mainboard.asl

@@ -15,15 +15,6 @@
  * GNU General Public License for more details.
  */
 
-Scope (\_SB)
-{
-	Device (PWRB)
-	{
-		Name (_HID, EisaId ("PNP0C0C"))
-		Name (_UID, 1)
-	}
-}
-
 /*
  * Onboard CPLD
  */