soc/intel/pantherlake: Update IGD stolen memory size definitions

Update the Integrated Graphics Device (IGD) stolen memory size enum
values to align with the Panther Lake Reference Code. This change
introduces the 96MB definition and corrects the value for 128MB.

Modified values:
- IGD_SM_96MB:  Added as 0x03
- IGD_SM_128MB: Updated from 0x03 to 0x04

Change-Id: Id7a547e8a530294a76f201e87865e8508ff67a92
Signed-off-by: Subrata Banik <subratabanik@google.com>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/91140
Reviewed-by: Jérémy Compostella <jeremy.compostella@intel.com>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>

src/soc/intel/pantherlake/chip.h

@@ -337,7 +337,8 @@ struct soc_intel_pantherlake_config {
 		IGD_SM_0MB = 0x00,
 		IGD_SM_32MB = 0x01,
 		IGD_SM_64MB = 0x02,
-		IGD_SM_128MB = 0x03,
+		IGD_SM_96MB = 0x03,
+		IGD_SM_128MB = 0x04,
 		IGD_SM_4MB = 0xF0,
 		IGD_SM_8MB = 0xF1,
 		IGD_SM_12MB = 0xF2,