x86/platform/intel/quark: Explicitly include linux/io.h for virt_to_phys()

Similarly to the previous patches by Sean Christopherson:

 "Through a labyrinthian sequence of includes, usage of virt_to_phys() is
  dependent on the include of asm/io.h in x86's asm/realmode.h, which is
  included in x86's asm/acpi.h and thus by linux/acpi.h.  Explicitly
  include linux/io.h to break the dependency on realmode.h so that a
  future patch can remove the realmode.h include from acpi.h without
  breaking the build."

Reviewed-by: Andy Shevchenko <andy.shevchenko@gmail.com>
Cc: linux-kernel@vger.kernel.org
Cc: Sean Christopherson <sean.j.christopherson@intel.com>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Ingo Molnar <mingo@kernel.org>