splice, tee: Move splice.h tee.h to include/lapi

Move the function definitions to global header because the tee01 needs
splice() too.

Signed-off-by: Cyril Hrubis <chrubis@suse.cz>
include/lapi/fcntl.h: Add splice() flags + include

* Add SPLICE_F_NONBLOCK to lapi/fcntl.h

* Include lapi/splice.h lapi/tee.h in lapi/fcntl.h

Signed-off-by: Cyril Hrubis <chrubis@suse.cz>
syscalls/tee01: Cleanup & fixes.

* Use tst_exit() instead of return (0)
  (the possible test failure is propagated now)

* Use SAFE_MACROS()

* Remove useless comments

* ...

Signed-off-by: Cyril Hrubis <chrubis@suse.cz>