misc/pvpanic: add MMIO support

On some architectures (e.g. arm64), it's preferable to use MMIO, since
this can be used standalone. Add MMIO support to the pvpanic driver.

Suggested-by: Andy Shevchenko <andy.shevchenko@gmail.com>
[Use acpi_dev_resource_memory API. - Andy]
Reviewed-by: Andy Shevchenko <andy.shevchenko@gmail.com>
Acked-by: Mark Rutland <mark.rutland@arm.com>
Signed-off-by: Peng Hao <peng.hao2@zte.com.cn>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>