init/: remove ineffective sparse disabling

Sparse checking used to be disabled on init/do_mounts.c and a few related
files because "Many of the syscalls used in this file expect some of the
arguments to be __user pointers not __kernel pointers".

However since 28128c61 ("kconfig.h: Include compiler types to avoid
missed struct attributes") the checks are, in fact, not disabled anymore
because of the more early include of "linux/compiler_types.h"

So remove the now ineffective #undefery that was done to disable these
warnings, as well as the associated comment.

Link: http://lkml.kernel.org/r/20180617115355.53799-1-luc.vanoostenryck@gmail.comSigned-off-by: NLuc Van Oostenryck <luc.vanoostenryck@gmail.com>
Cc: Dominik Brodowski <linux@dominikbrodowski.net>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Kees Cook <keescook@chromium.org>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

init/do_mounts.c

-/*
- * Many of the syscalls used in this file expect some of the arguments
- * to be __user pointers not __kernel pointers.  To limit the sparse
- * noise, turn off sparse checking for this file.
- */
-#ifdef __CHECKER__
-#undef __CHECKER__
-#warning "Sparse checking disabled for this file"
-#endif
-
 #include <linux/module.h>
 #include <linux/sched.h>
 #include <linux/ctype.h>

init/do_mounts_initrd.c

 // SPDX-License-Identifier: GPL-2.0
-/*
- * Many of the syscalls used in this file expect some of the arguments
- * to be __user pointers not __kernel pointers.  To limit the sparse
- * noise, turn off sparse checking for this file.
- */
-#ifdef __CHECKER__
-#undef __CHECKER__
-#warning "Sparse checking disabled for this file"
-#endif
-
 #include <linux/unistd.h>
 #include <linux/kernel.h>
 #include <linux/fs.h>

init/do_mounts_md.c

 // SPDX-License-Identifier: GPL-2.0
-/*
- * Many of the syscalls used in this file expect some of the arguments
- * to be __user pointers not __kernel pointers.  To limit the sparse
- * noise, turn off sparse checking for this file.
- */
-#ifdef __CHECKER__
-#undef __CHECKER__
-#warning "Sparse checking disabled for this file"
-#endif
-
 #include <linux/delay.h>
 #include <linux/raid/md_u.h>
 #include <linux/raid/md_p.h>

init/do_mounts_rd.c

 // SPDX-License-Identifier: GPL-2.0
-/*
- * Many of the syscalls used in this file expect some of the arguments
- * to be __user pointers not __kernel pointers.  To limit the sparse
- * noise, turn off sparse checking for this file.
- */
-#ifdef __CHECKER__
-#undef __CHECKER__
-#warning "Sparse checking disabled for this file"
-#endif
-
 #include <linux/kernel.h>
 #include <linux/fs.h>
 #include <linux/minix_fs.h>

init/initramfs.c

 // SPDX-License-Identifier: GPL-2.0
-/*
- * Many of the syscalls used in this file expect some of the arguments
- * to be __user pointers not __kernel pointers.  To limit the sparse
- * noise, turn off sparse checking for this file.
- */
-#ifdef __CHECKER__
-#undef __CHECKER__
-#warning "Sparse checking disabled for this file"
-#endif
-
 #include <linux/init.h>
 #include <linux/fs.h>
 #include <linux/slab.h>