uapi: add INT_MAX and INT_MIN constants

Some UAPI headers use INT_MAX and INT_MIN. Currently they include
<limits.h> for their definitions, which introduces a problematic
dependency on libc.

Add custom, namespaced definitions of INT_MAX and INT_MIN using the
same values as the regular kernel code.
These definitions are not added to uapi/linux/limits.h, as that header
will conflict with libc definitions on some platforms.

Signed-off-by: Thomas Weißschuh <[e-mail]>
Link: https://patch.msgid.link/[e-mail]
Signed-off-by: Jakub Kicinski <[e-mail]>

include/uapi/linux/typelimits.h

···
+/* SPDX-License-Identifier: GPL-2.0 WITH Linux-syscall-note */
+#ifndef _UAPI_LINUX_TYPELIMITS_H
+#define _UAPI_LINUX_TYPELIMITS_H
+
+#define __KERNEL_INT_MAX ((int)(~0U >> 1))
+#define __KERNEL_INT_MIN (-__KERNEL_INT_MAX - 1)
+
+#endif /* _UAPI_LINUX_TYPELIMITS_H */