ipc/shm: uapi: remove dependency on libc

Using libc types and headers from the UAPI headers is problematic as it
introduces a dependency on a full C toolchain. shm.h does not even use
any symbols from the libc header as the usage of getpagesize() was removed
a decade ago in commit 060028bac94b ("ipc/shm.c: increase the defaults for
SHMALL, SHMMAX")

Drop the unnecessary inclusion.

Link: https://lkml.kernel.org/r/[e-mail]
Signed-off-by: Thomas Weißschuh <[e-mail]>
Cc: Arnd Bergmann <[e-mail]>
Signed-off-by: Andrew Morton <[e-mail]>

include/uapi/linux/shm.h

···
 #include <linux/ipc.h>
 #include <linux/errno.h>
 #include <asm-generic/hugetlb_encode.h>
-#ifndef __KERNEL__
-#include <unistd.h>
-#endif
 
 /*
  * SHMMNI, SHMMAX and SHMALL are default upper limits which can be