Modify ppe trace prefix to have same trace hash for DD1 and DD2

Change-Id: Ic8b7223b7de6b22fe42b12e9208f0fac7a36cfe9
Reviewed-on: http://ralgit01.raleigh.ibm.com/gerrit1/40263
Tested-by: Jenkins Server <pfd-jenkins+hostboot@us.ibm.com>
Tested-by: FSP CI Jenkins <fsp-CI-jenkins+hostboot@us.ibm.com>
Reviewed-by: Sachin Gupta <sgupta2m@in.ibm.com>
Reviewed-by: AMIT J. TENDOLKAR <amit.tendolkar@in.ibm.com>

src/build/img_defs.mk

@@ -376,7 +376,7 @@ endif
 # Generate a 16bit trace string hash prefix value based on the name of this image.  This will form
 # the upper 16 bits of the 32 bit trace hash values.
 ifndef PK_TRACE_HASH_PREFIX
-PK_TRACE_HASH_PREFIX := $(shell echo $(IMAGE_SEEPROM_NAME) | md5sum | cut -c1-4 | xargs -i printf "%d" 0x{})
+PK_TRACE_HASH_PREFIX := $(shell echo "SBE_MAIN" | md5sum | cut -c1-4 | xargs -i printf "%d" 0x{})
 endif
 
 ifndef GCC-O-LEVEL