printk: Move back proc_dointvec_minmax_sysadmin() to sysctl.c

printk: Move back proc_dointvec_minmax_sysadmin() to sysctl.c

The proc_dointvec_minmax_sysadmin() helper is useful for the
fs.trusted_for_policy sysctl brought by the next commit.

This partially revert commit faaa357a55e0 ("printk: move printk sysctl
to printk/sysctl.c") to share the proc_dointvec_minmax_sysadmin()
helper.

Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Luis Chamberlain <mcgrof@kernel.org>
Cc: Xiaoming Ni <nixiaoming@huawei.com>
Link: https://lore.kernel.org/r/20220104155024.48023-2-mic@digikod.net
[mic: update according to new commit 1f2cfdd349b7 ("printk: Fix
incorrect __user type in proc_dointvec_minmax_sysadmin()")]
Signed-off-by: Mickaël Salaün <mic@linux.microsoft.com>