x86-64, kcmp: The kcmp system call can be common

We already use the same system call handler for i386 and x86-64, there
is absolutely no reason x32 can't use the same system call, too.

Signed-off-by: H. Peter Anvin <hpa@linux.intel.com>
Cc: H.J. Lu <hjl.tools@gmail.com>
Cc: Cyrill Gorcunov <gorcunov@openvz.org>
Cc: <stable@vger.kernel.org> v3.5
Link: http://lkml.kernel.org/n/tip-vwzk3qbcr3yjyxjg2j38vgy9@git.kernel.org

arch/x86/syscalls/syscall_64.tbl

@@ -318,7 +318,7 @@
 309	common	getcpu			sys_getcpu
 310	64	process_vm_readv	sys_process_vm_readv
 311	64	process_vm_writev	sys_process_vm_writev
-312	64	kcmp			sys_kcmp
+312	common	kcmp			sys_kcmp
 
 #
 # x32-specific system call numbers start at 512 to avoid cache impact