ARM: uniphier: allow debug_ll_init() to do nothing for unknown SoCs

This function should just return for unknown SoCs rather than writing
unexpected values to registers.

Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
diff --git a/arch/arm/mach-uniphier/arm32/debug_ll.S b/arch/arm/mach-uniphier/arm32/debug_ll.S
index a70954c..8e4943c 100644
--- a/arch/arm/mach-uniphier/arm32/debug_ll.S
+++ b/arch/arm/mach-uniphier/arm32/debug_ll.S
@@ -175,6 +175,7 @@
 	b		init_uart
 ph1_ld6b_end:
 #endif
+	mov		pc, lr
 
 init_uart:
 	addruart	r0, r1, r2