tools/nolibc: don't use asm/ UAPI headers

The asm/ and asm-generic/ namespaces are implementation details of the UAPI
headers and not meant for direct usage.

Use the equivalent headers from the linux/ namespace instead.

While at it also drop the duplicate include of linux/signal.h from sys.h.

Signed-off-by: Thomas Weißschuh <thomas.weissschuh@linutronix.de>
Link: https://lore.kernel.org/r/20250307-nolibc-asm-headers-v2-1-e2a734f25d22@linutronix.de

Author: t-8ch

tools/include/nolibc/arch-s390.h

@@ -5,8 +5,8 @@
 
 #ifndef _NOLIBC_ARCH_S390_H
 #define _NOLIBC_ARCH_S390_H
-#include <asm/signal.h>
-#include <asm/unistd.h>
+#include <linux/signal.h>
+#include <linux/unistd.h>
 
 #include "compiler.h"
 #include "crt.h"

tools/include/nolibc/errno.h

@@ -7,7 +7,7 @@
 #ifndef _NOLIBC_ERRNO_H
 #define _NOLIBC_ERRNO_H
 
-#include <asm/errno.h>
+#include <linux/errno.h>
 
 #ifndef NOLIBC_IGNORE_ERRNO
 #define SET_ERRNO(v) do { errno = (v); } while (0)

tools/include/nolibc/sys.h

@@ -10,10 +10,10 @@
 #include "std.h"
 
 /* system includes */
-#include <asm/unistd.h>
-#include <asm/signal.h>  /* for SIGCHLD */
-#include <asm/ioctls.h>
-#include <asm/mman.h>
+#include <linux/unistd.h>
+#include <linux/signal.h>  /* for SIGCHLD */
+#include <linux/termios.h>
+#include <linux/mman.h>
 #include <linux/fs.h>
 #include <linux/loop.h>
 #include <linux/time.h>
@@ -23,7 +23,6 @@
 #include <linux/prctl.h>
 #include <linux/resource.h>
 #include <linux/utsname.h>
-#include <linux/signal.h>
 
 #include "arch.h"
 #include "errno.h"