intel-mid: sfi: Allow struct devs_id.get_platform_data to be NULL

Intel mid sfi code doesn't need struct devs_id.get_platform_data != NULL.
If the callback is not set, just assume there is no platform_data.

Signed-off-by: David Cohen <david.a.cohen@linux.intel.com>
Link: http://lkml.kernel.org/r/1382049336-21316-11-git-send-email-david.a.cohen@linux.intel.com
Cc: Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@linux.intel.com>
Signed-off-by: H. Peter Anvin <hpa@linux.intel.com>