ray_cs: Add include guards

The files ray_cs.h and rayctl.h both contain two thirds of what
appears to be an include guard using the macro name RAYLINK_H (both
lack the #define). Since RAYLINK_H is not defined anywhere, the
#ifndefs are confusing no-ops. Add proper include guards using
different macro names.

Signed-off-by: Rasmus Villemoes <linux@rasmusvillemoes.dk>
Signed-off-by: John W. Linville <linville@tuxdriver.com>