headers: Unbreak some ARM syscalls

Restore the outside-kernel exclusion for some syscalls that was
removed by change I959b64280e184655ef8c713aa79f9e23cb1f7df4,
since these syscalls are used elsewhere.

Change-Id: I5b5bf3d78edd137e820d25281a375966b6c009ec
diff --git a/libc/kernel/arch-arm/asm/unistd.h b/libc/kernel/arch-arm/asm/unistd.h
index 454ed89..b3d75ca 100644
--- a/libc/kernel/arch-arm/asm/unistd.h
+++ b/libc/kernel/arch-arm/asm/unistd.h
@@ -466,7 +466,7 @@
 #define __ARM_NR_usr32 (__ARM_NR_BASE+4)
 #define __ARM_NR_set_tls (__ARM_NR_BASE+5)
 /* WARNING: DO NOT EDIT, AUTO-GENERATED CODE - SEE TOP FOR INSTRUCTIONS */
-#ifdef __ARM_EABI__
+#if defined(__ARM_EABI__) && !defined(__KERNEL__)
 #undef __NR_time
 #undef __NR_umount
 #undef __NR_stime