soc/intel/common/block/acpi: Factor out common gfx.asl

This patch moves gfx.asl into common block acpi directory to
avoid duplicating the same ASL code block across SoC directory.

TEST=Able to build and boot CML platform.
1) Dump and disassemble DSDT, verify GFX0 device present inside
common gfx.asl is still there.
2) Verify no ACPI error seen while running 'dmesg` from console.

Signed-off-by: Subrata Banik <subrata.banik@intel.com>
Change-Id: Ie34181a6783d348265cf4299dec5c41e7f4f736f
Reviewed-on: https://review.coreboot.org/c/coreboot/+/45997
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Duncan Laurie <dlaurie@chromium.org>
Reviewed-by: Angel Pons <th3fanbus@gmail.com>

src/soc/intel/cannonlake/acpi/southbridge.asl

@@ -17,7 +17,7 @@
 #endif
 
 /* GFX 00:02.0 */
-#include "gfx.asl"
+#include <soc/intel/common/block/acpi/acpi/gfx.asl>
 
 /* LPC 0:1f.0 */
 #include <soc/intel/common/block/acpi/acpi/lpc.asl>