x86/power/64: Use struct desc_ptr for the IDT in struct saved_context

x86_64's saved_context nonsensically used separate idt_limit and
idt_base fields and then cast &idt_limit to struct desc_ptr *.

This was correct (with -fno-strict-aliasing), but it's confusing,
served no purpose, and required #ifdeffery. Simplify this by
using struct desc_ptr directly.

No change in functionality.

Tested-by: Jarkko Nikula <jarkko.nikula@linux.intel.com>
Signed-off-by: Andy Lutomirski <luto@kernel.org>
Acked-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Acked-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Borislav Petkov <bpetkov@suse.de>
Cc: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Pavel Machek <pavel@ucw.cz>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Rafael J. Wysocki <rjw@rjwysocki.net>
Cc: Zhang Rui <rui.zhang@intel.com>
Link: http://lkml.kernel.org/r/967909ce38d341b01d45eff53e278e2728a3a93a.1513286253.git.luto@kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>

arch/x86/include/asm/suspend_64.h

@@ -30,8 +30,7 @@ struct saved_context {
 	u16 gdt_pad; /* Unused */
 	struct desc_ptr gdt_desc;
 	u16 idt_pad;
-	u16 idt_limit;
-	unsigned long idt_base;
+	struct desc_ptr idt;
 	u16 ldt;
 	u16 tss;
 	unsigned long tr;

arch/x86/power/cpu.c

@@ -82,12 +82,8 @@ static void __save_processor_state(struct saved_context *ctxt)
 	/*
 	 * descriptor tables
 	 */
-#ifdef CONFIG_X86_32
 	store_idt(&ctxt->idt);
-#else
-/* CONFIG_X86_64 */
-	store_idt((struct desc_ptr *)&ctxt->idt_limit);
-#endif
+
 	/*
 	 * We save it here, but restore it only in the hibernate case.
 	 * For ACPI S3 resume, this is loaded via 'early_gdt_desc' in 64-bit
@@ -219,12 +215,7 @@ static void notrace __restore_processor_state(struct saved_context *ctxt)
 	 * now restore the descriptor tables to their proper values
 	 * ltr is done i fix_processor_context().
 	 */
-#ifdef CONFIG_X86_32
 	load_idt(&ctxt->idt);
-#else
-/* CONFIG_X86_64 */
-	load_idt((const struct desc_ptr *)&ctxt->idt_limit);
-#endif
 
 #ifdef CONFIG_X86_64
 	/*