Use the correct names for the __ARM_NR_* syscalls.

This lets us move all the ARM syscall stubs over to the kernel <asm/unistd.h>.
Our generated <sys/linux-syscalls.h> is now unused, but I'll remove that in a
later change.

Change-Id: Ie5ff2cc4abce1938576af7cbaef615a79c7f310d
diff --git a/libc/arch-arm/syscalls/socketpair.S b/libc/arch-arm/syscalls/socketpair.S
index da40cd6..0e4db77 100644
--- a/libc/arch-arm/syscalls/socketpair.S
+++ b/libc/arch-arm/syscalls/socketpair.S
@@ -1,7 +1,7 @@
 /* autogenerated by gensyscalls.py */
+#include <asm/unistd.h>
 #include <linux/err.h>
 #include <machine/asm.h>
-#include <sys/linux-syscalls.h>
 
 ENTRY(socketpair)
     mov     ip, r7