Correct whitelist generated source file extension

Change-Id: I9480ef48c410708cf2b5fb97c4ac93ef486c6cd2
Signed-off-by: Matthew Barth <msbarth@us.ibm.com>
diff --git a/Makefile b/Makefile
index 8652658..cdb396b 100644
--- a/Makefile
+++ b/Makefile
@@ -45,7 +45,7 @@
 INCLUDEDIR ?= /usr/include
 LIBDIR ?= /usr/lib
 
-WHITELIST_SRC = ipmiwhitelist.C
+WHITELIST_SRC = ipmiwhitelist.cpp
 WHITELIST_CONF ?= host-ipmid-whitelist.conf
 
 all: $(DAEMON) $(LIB_APP) $(LIB_HOST_SRV) $(TESTER)