soc/intel/xeon_sp/skx: Fix uncore.asl \_SB namespace issue

The skx uncore ACPI scope was missing the \ on \_SB causing
the uncore IRQs to not be in the namespace. This addresses
ACPI uncore IRQ routing issues. This was found preparing
skx acpi to match cpx acpi for merging in the future.

Check scope in dsdt.asl in tiogapass build.

Change-Id: I799042babbe60287e5e4ec60b21c08d57ccda04b
Signed-off-by: Marc Jones <marcjones@sysproconsulting.com>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/45269
Reviewed-by: HAOUAS Elyes <ehaouas@noos.fr>
Reviewed-by: Angel Pons <th3fanbus@gmail.com>
Reviewed-by: Maxim Polyakov <max.senia.poliak@gmail.com>
Reviewed-by: Jay Talbott <JayTalbott@sysproconsulting.com>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>

src/soc/intel/xeon_sp/skx/acpi/uncore.asl

@@ -25,7 +25,7 @@ Scope(\)
 	}
 }
 
-Scope (_SB)
+Scope (\_SB)
 {
 	#include "pci_irq.asl"
 	#include "uncore_irq.asl"