sh: Fix up stack debugging build.

Somewhere along the line the ebss label was taken out, resulting in pcrel
branch too far errors. Restore the label to get things building again.
Signed-off-by: Paul Mundt <lethal@linux-sh.org>

arch/sh/lib/mcount.S

@@ -294,6 +294,8 @@ stack_panic:
 	.align 2
 .L_init_thread_union:
 	.long	init_thread_union
+.L_ebss:
+	.long	__bss_stop
 .Lpanic:
 	.long	panic
 .Lpanic_s: