arm64: remove CONFIG_VMAP_STACK conditionals from traps overflow stack

With VMAP_STACK now always enabled on arm64, remove the
CONFIG_VMAP_STACK checks from overflow stack definitions and related
code in arch/arm64/kernel/traps.c. The overflow_stack and
panic_bad_stack() logic are now unconditionally included, simplifying
the source and matching the mandatory stack model.

Signed-off-by: Breno Leitao <[e-mail]>
Acked-by: Ard Biesheuvel <[e-mail]>
Acked-by: Mark Rutland <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Will Deacon <[e-mail]>

arch/arm64/kernel/traps.c

···
 			      "Bad EL0 synchronous exception");
 }
 
-#ifdef CONFIG_VMAP_STACK
-
 DEFINE_PER_CPU(unsigned long [OVERFLOW_STACK_SIZE/sizeof(long)], overflow_stack)
 	__aligned(16);
 
···
 	nmi_panic(NULL, "kernel stack overflow");
 	cpu_park_loop();
 }
-#endif
 
 void __noreturn arm64_serror_panic(struct pt_regs *regs, unsigned long esr)
 {