avr32: use generic gd->start_addr_sp

Before avr32 had an extra storage for stack end to have a nice stack printout
on exception. Remove this extra storage and use generic gd->start_addr_sp
instead.

Signed-off-by: Andreas Bießmann <andreas.devel@googlemail.com>
diff --git a/arch/avr32/cpu/exception.c b/arch/avr32/cpu/exception.c
index 5d1bc68..d6991f6 100644
--- a/arch/avr32/cpu/exception.c
+++ b/arch/avr32/cpu/exception.c
@@ -96,11 +96,11 @@
 	printf("CPU Mode: %s\n", cpu_modes[mode]);
 
 	/* Avoid exception loops */
-	if (regs->sp < (gd->arch.stack_end - CONFIG_STACKSIZE)
-			|| regs->sp >= gd->arch.stack_end)
+	if (regs->sp < (gd->start_addr_sp - CONFIG_STACKSIZE) ||
+	    regs->sp >= gd->start_addr_sp)
 		printf("\nStack pointer seems bogus, won't do stack dump\n");
 	else
-		dump_mem("\nStack: ", regs->sp, gd->arch.stack_end);
+		dump_mem("\nStack: ", regs->sp, gd->start_addr_sp);
 
 	panic("Unhandled exception\n");
 }