Always include <sys/...>, not <linux/...>.

Change-Id: I1d1d569d704485dd48e70da1927de95263db4fb6
diff --git a/dhcpcd.c b/dhcpcd.c
index bac33f3..6eae970 100644
--- a/dhcpcd.c
+++ b/dhcpcd.c
@@ -74,7 +74,7 @@
 
 #ifdef ANDROID
 #include <sys/capability.h>
-#include <linux/prctl.h>
+#include <sys/prctl.h>
 #include <cutils/properties.h>
 #include <private/android_filesystem_config.h>
 #endif