Clean up <sched.h>.

This patch switches to using the uapi constants. It also adds the missing
setns system call, fixes sched_getcpu's error behavior, and fixes the
gensyscalls script now ARM is uapi-only too.

Change-Id: I8e16b1693d6d32cd9b8499e46b5d8b0a50bc4f1d
diff --git a/libc/Android.mk b/libc/Android.mk
index 7c098a8..1164bd6 100644
--- a/libc/Android.mk
+++ b/libc/Android.mk
@@ -112,7 +112,6 @@
 	bionic/recv.c \
 	bionic/sched_cpualloc.c \
 	bionic/sched_cpucount.c \
-	bionic/sched_getcpu.c \
 	bionic/semaphore.c \
 	bionic/send.c \
 	bionic/setpgrp.c \
@@ -261,6 +260,7 @@
     bionic/sbrk.cpp \
     bionic/scandir.cpp \
     bionic/sched_getaffinity.cpp \
+    bionic/sched_getcpu.cpp \
     bionic/setegid.cpp \
     bionic/__set_errno.cpp \
     bionic/seteuid.cpp \