msm8953 & msm8996 : Append "rootfstype=" and "root=" to kernel command line

This change is to get the system partition index and append it to kernel
command line instead of hardcoding the value in .conf files
used during the LE build process

Change-Id: I1b9e7744e0b95246e45911682cbb5c3ff61e9dab
diff --git a/project/msm8996.mk b/project/msm8996.mk
index baefdf8..de818bb 100644
--- a/project/msm8996.mk
+++ b/project/msm8996.mk
@@ -109,6 +109,10 @@
 DEFINES += LPAE=1
 endif
 
+ifeq ($(APPEND_CMDLINE),1)
+DEFINES += _APPEND_CMDLINE=1
+endif
+
 CFLAGS += -Werror
 
 #enable user force reset feature