Correct SH kernel-features.h undefines (bug 23862)

[Florian Weimer]

* Joseph Myers:

> 	[BZ #23862]
> 	* sysdeps/unix/sysv/linux/sh/kernel-features.h
> 	[__LINUX_KERNEL_VERSION < 0x040800] (__ASSUME_EXECVEAT): Undefine.
> 	[__LINUX_KERNEL_VERSION < 0x040800] (__ASSUME_MLOCK2): Likewise.
> 	[__LINUX_KERNEL_VERSION < 0x040800] (__ASSUME_COPY_FILE_RANGE):
> 	Likewise.

This looks okay based on this kernel commit:

commit 74bdaa611fa69368fb4032ad437af073d31116bd
Author: Yoshinori Sato <ysato@users.sourceforge.jp>
Date:   Tue Jun 28 15:49:46 2016 +0900

    sh: system call wire up

Thanks,
Florian