x32: Add x32 system calls to syscall/syscall_64.tbl

Split the 64-bit system calls into "64" (64-bit only) and "common"
(64-bit or x32) and add the x32 system call numbers.

Signed-off-by: H. Peter Anvin <hpa@zytor.com>
diff --git a/arch/x86/syscalls/Makefile b/arch/x86/syscalls/Makefile
index 564b247..89dd958 100644
--- a/arch/x86/syscalls/Makefile
+++ b/arch/x86/syscalls/Makefile
@@ -24,7 +24,7 @@
 $(out)/unistd_32_ia32.h: $(syscall32) $(syshdr)
 	$(call if_changed,syshdr)
 
-syshdr_abi_unistd_64 := 64
+syshdr_abi_unistd_64 := common,64
 $(out)/unistd_64.h: $(syscall64) $(syshdr)
 	$(call if_changed,syshdr)