x86/vdso: Add PUT_LE to store little-endian values

Add PUT_LE() by analogy with GET_LE() to write littleendian values in
addition to reading them.

Signed-off-by: Andy Lutomirski <luto@amacapital.net>
Link: http://lkml.kernel.org/r/3d9b27e92745b27b6fda1b9a98f70dc9c1246c7a.1402620737.git.luto@amacapital.net


Signed-off-by: H. Peter Anvin <hpa@zytor.com>