sysinfo: Move struct sysinfo to a separate header file

struct sysinfo is just about the only thing exported to userspace from
<linux/kernel.h>, so move it into a separate header file with a
residual #include in <linux/kernel.h>.

Originally-by: H. J. Lu <hjl.tools@gmail.com>
Signed-off-by: H. Peter Anvin <hpa@zytor.com>
Link: http://lkml.kernel.org/n/tip-4pr1xnnksprt7t0h3w5fw4rv@git.kernel.org
diff --git a/include/linux/Kbuild b/include/linux/Kbuild
index c94e717..8446086 100644
--- a/include/linux/Kbuild
+++ b/include/linux/Kbuild
@@ -355,6 +355,7 @@
 header-y += swab.h
 header-y += synclink.h
 header-y += sysctl.h
+header-y += sysinfo.h
 header-y += taskstats.h
 header-y += tcp.h
 header-y += telephony.h