linux-musl-s390x: Remove bogus definition of O_FSYNC

musl-libc does not define O_FSYNC on any architecture, since commit
v1.1.15-15-gc1f4ed15 (committed 2016-08-30):

  https://git.musl-libc.org/cgit/musl/commit/?id=c1f4ed150137d793c9d07356305a89e8785e7e02

Fixes: 88de388 ("add definitions for s390x musl targets")

Author: neuschaefer

src/unix/linux_like/linux/musl/b64/s390x.rs

@@ -133,7 +133,6 @@ pub const O_NOCTTY: c_int = 256;
 pub const O_SYNC: c_int = 1052672;
 pub const O_RSYNC: c_int = 1052672;
 pub const O_DSYNC: c_int = 4096;
-pub const O_FSYNC: c_int = 0x101000;
 pub const O_DIRECT: c_int = 0x4000;
 pub const O_DIRECTORY: c_int = 0x10000;
 pub const O_NOFOLLOW: c_int = 0x20000;