tools/nolibc: sys.h: apply __sysret() helper

Use __sysret() to shrink most of the library routines to oneline code.

Removed 266 lines of duplicated code.

Reviewed-by: Thomas Weißschuh <[email protected]>
Signed-off-by: Zhangjin Wu <[email protected]>
Signed-off-by: Willy Tarreau <[email protected]>

Author: lzufalcon