CMakeLists.txt: s/MCTP_FILEIO/MCTP_HAVE_FILEIO

Definition name was wrong.

Change-Id: Ia0b7a3b1196a5aef9c01341c62453e2a2b276f27
Signed-off-by: James Feist <james.feist@linux.intel.com>
diff --git a/CMakeLists.txt b/CMakeLists.txt
index a5b1042..ef7506f 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -1,7 +1,7 @@
 cmake_minimum_required (VERSION 3.5 FATAL_ERROR)
 
 add_definitions (-DMCTP_LOG_STDERR)
-add_definitions (-DMCTP_FILEIO)
+add_definitions (-DMCTP_HAVE_FILEIO)
 
 add_library (libmctp STATIC alloc.c core.c log.c libmctp.h serial.c)