Rename ARM's regs structure to arm_regs

Compile-tested.

* defs.h: Rename regs structure to arm_regs.
* syscall.c: Likewise.
(printcall): Use new name instead of old one.
(get_regs): Likewise.
(get_scno): Likewise.
(get_syscall_args): Likewise.
(get_error): Likewise.
* signal.c (sys_sigreturn): Likewise.

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
diff --git a/signal.c b/signal.c
index 0cb25e2..4dbf8b4 100644
--- a/signal.c
+++ b/signal.c
@@ -884,7 +884,7 @@
 	if (entering(tcp)) {
 		struct sigcontext_struct sc;
 		sigset_t sigm;
-		if (umove(tcp, regs.ARM_sp, &sc) < 0)
+		if (umove(tcp, arm_regs.ARM_sp, &sc) < 0)
 			return 0;
 		long_to_sigset(sc.oldmask, &sigm);
 		tprints(sprintsigmask(") (mask ", &sigm, 0));