x86: ksysfs.c build fix

kbuild test robot report below error for randconfig:

  arch/x86/kernel/ksysfs.c: In function 'get_setup_data_paddr':
  arch/x86/kernel/ksysfs.c:81:3: error: implicit declaration of function 'ioremap_cache' [-Werror=implicit-function-declaration]
  arch/x86/kernel/ksysfs.c:86:3: error: implicit declaration of function 'iounmap' [-Werror=implicit-function-declaration]

Fix it by including <asm/io.h> in ksysfs.c

Signed-off-by: Dave Young <dyoung@redhat.com>
Signed-off-by: Matt Fleming <matt.fleming@intel.com>