control: Remove msgbuf.h dependency

We don't use any msgbuf definitions in the control protocol code, but do
rely on it pulling-in errno.h.

Remove msgbuf.h and include errno.h directly for the E<thing> constants.

Change-Id: I4dbae12fbc15c6cd43158ecad3e06b977d17f67a
Signed-off-by: Jeremy Kerr <jk@codeconstruct.com.au>
diff --git a/src/control.c b/src/control.c
index f9b1c59..2056a0a 100644
--- a/src/control.c
+++ b/src/control.c
@@ -1,3 +1,4 @@
+#include <errno.h>
 #include <stdint.h>
 #include <stdbool.h>
 #include <string.h>
@@ -7,7 +8,6 @@
 #include <libpldm/platform.h>
 #include <libpldm/control.h>
 #include <compiler.h>
-#include <msgbuf.h>
 
 #include "control-internal.h"