get_regs: define for all architectures

* defs.h (get_regs_error): Remove.
(clear_regs): Update prototype, declare unconditionally.
(get_regs): Declare unconditionally.
* syscall.c (clear_regs): New function.
(get_regs): Define unconditionally.
(get_regs_error): Define unconditionally, change scope to static.
diff --git a/syscall.c b/syscall.c
index a355367..8929a75 100644
--- a/syscall.c
+++ b/syscall.c
@@ -791,6 +791,8 @@
 # define ARCH_REGS_FOR_GETREGSET arc_regs
 #endif
 
+static long get_regs_error;
+
 void
 print_pc(struct tcb *tcp)
 {
@@ -1017,8 +1019,11 @@
 }
 #endif
 
-#ifndef get_regs
-long get_regs_error;
+void
+clear_regs(void)
+{
+	get_regs_error = -1;
+}
 
 #if defined ARCH_REGS_FOR_GETREGSET
 static long
@@ -1116,7 +1121,6 @@
 	get_regs_error = 0;
 #endif
 }
-#endif /* !get_regs */
 
 /* Returns:
  * 0: "ignore this ptrace stop", bail out of trace_syscall_entering() silently.