arm64: hibernate: Avoid sending cross-calling with interrupts disabled

Since commit 3b8c9f1c ("arm64: IPI each CPU after invalidating the
I-cache for kernel mappings"), a call to flush_icache_range() will use
an IPI to cross-call other online CPUs so that any stale instructions
are flushed from their pipelines. This triggers a WARN during the
hibernation resume path, where flush_icache_range() is called with
interrupts disabled and is therefore prone to deadlock:

  | Disabling non-boot CPUs ...
  | CPU1: shutdown
  | psci: CPU1 killed.
  | CPU2: shutdown
  | psci: CPU2 killed.
  | CPU3: shutdown
  | psci: CPU3 killed.
  | WARNING: CPU: 0 PID: 1 at ../kernel/smp.c:416 smp_call_function_many+0xd4/0x350
  | Modules linked in:
  | CPU: 0 PID: 1 Comm: swapper/0 Not tainted 4.20.0-rc4 #1

Since all secondary CPUs have been taken offline prior to invalidating
the I-cache, there's actually no need for an IPI and we can simply call
__flush_icache_range() instead.

Cc: <stable@vger.kernel.org>
Fixes: 3b8c9f1c ("arm64: IPI each CPU after invalidating the I-cache for kernel mappings")
Reported-by: NKunihiko Hayashi <hayashi.kunihiko@socionext.com>
Tested-by: NKunihiko Hayashi <hayashi.kunihiko@socionext.com>
Tested-by: NJames Morse <james.morse@arm.com>
Signed-off-by: NWill Deacon <will.deacon@arm.com>
Signed-off-by: NCatalin Marinas <catalin.marinas@arm.com>

arch/arm64/kernel/hibernate.c

@@ -214,7 +214,7 @@ static int create_safe_exec_page(void *src_start, size_t length,
 	}
 
 	memcpy((void *)dst, src_start, length);
-	flush_icache_range(dst, dst + length);
+	__flush_icache_range(dst, dst + length);
 
 	pgdp = pgd_offset_raw(allocator(mask), dst_addr);
 	if (pgd_none(READ_ONCE(*pgdp))) {