misra: add missing noreturn attribute for __div0()

The __div0() function never returns to its caller, causing a violation
of MISRA C Rule 2.1: "A project shall not contain unreachable code".
Add the `noreturn` attribute to fix this.

Signed-off-by: Dmytro Prokopchuk <dmytro_prokopchuk1@epam.com>
Reviewed-by: Nicola Vetrini <nicola.vetrini@bugseng.com>
Acked-by: Stefano Stabellini <sstabellini@kernel.org>

xen/arch/arm/traps.c

@@ -172,7 +172,7 @@ void init_traps(void)
     isb();
 }
 
-void asmlinkage __div0(void)
+void asmlinkage noreturn __div0(void)
 {
     printk("Division by zero in hypervisor.\n");
     BUG();