efi: rtc-efi: Export platform:rtc-efi as module alias
When the rtc-efi driver is built as a module, we already register the
EFI rtc as a platform device if UEFI Runtime Services are enabled.
To wire it up to udev, and let the module be loaded automatically, we
need to export the 'platform:rtc-efi' alias from the module.
Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org> Cc: Alessandro Zummo <a.zummo@towertech.it> Cc: Mark Salter <msalter@redhat.com> Cc: Dave Young <dyoung@redhat.com> Signed-off-by: Matt Fleming <matt.fleming@intel.com>