um/x86: merge (and trim) 32- and 64-bit variants of ptrace.h

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
diff --git a/arch/um/kernel/skas/syscall.c b/arch/um/kernel/skas/syscall.c
index f5173e1..05fbeb4 100644
--- a/arch/um/kernel/skas/syscall.c
+++ b/arch/um/kernel/skas/syscall.c
@@ -34,7 +34,7 @@
 		result = -ENOSYS;
 	else result = EXECUTE_SYSCALL(syscall, regs);
 
-	REGS_SET_SYSCALL_RETURN(r->gp, result);
+	UPT_SET_SYSCALL_RETURN(r, result);
 
 	syscall_trace(r, 1);
 }