xen/arm: traps: Don't panic when receiving an unknown debug trap

Even if debug trap are only meant for debugging purpose, it is quite
harsh to crash Xen if one of the trap sent by the guest is not handled.

So switch from a panic() to a printk().

Signed-off-by: Julien Grall <jgrall@amazon.com>
Reviewed-by: Stefano Stabellini <sstabellini@kernel.org>

xen/arch/arm/traps.c

@@ -1410,7 +1410,7 @@ static void do_debug_trap(struct cpu_user_regs *regs, unsigned int code)
         show_execution_state(regs);
         break;
     default:
-        panic("DOM%d: Unhandled debug trap %#x\n", domid, code);
+        printk("DOM%d: Unhandled debug trap %#x\n", domid, code);
         break;
     }
 }