x86-64, ia32: Move compat_ni_syscall into C and its own file

Move compat_ni_syscall out of ia32entry.S and into its own .c file.
Although this is a trivial function, it is not performance-critical,
and this will simplify further cleanups.

Signed-off-by: H. Peter Anvin <hpa@linux.intel.com>

arch/x86/ia32/nosyscall.c

@@ -0,0 +1,7 @@
+#include <linux/kernel.h>
+#include <linux/errno.h>
+
+long compat_ni_syscall(void)
+{
+	return -ENOSYS;
+}