lkl: silence undefined declartions

This commit add several definition to quiet compiler warnings during
tools build.

Signed-off-by: Hajime Tazaki <thehajime@gmail.com>

Author: thehajime

arch/lkl/include/uapi/asm/syscalls.h

@@ -75,6 +75,8 @@ typedef __s64			s64;
 #undef __NR_bdflush
 #undef __NR_send
 #undef __NR_recv
+#undef __NR_sysfs
+#undef __NR_signalfd
 
 #undef __NR_umount
 #define __NR_umount __NR_umount2
@@ -124,6 +126,10 @@ struct sockaddr {
 	char sa_data[14];
 };
 
+struct __aio_sigset;
+struct cachestat;
+struct cachestat_range;
+
 #define __UAPI_DEF_IF_NET_DEVICE_FLAGS_LOWER_UP_DORMANT_ECHO 1
 #define __UAPI_DEF_IF_IFNAMSIZ	1
 #define __UAPI_DEF_IF_NET_DEVICE_FLAGS 1