edd: don't spam log if no EDD information is present

We've had reports from users being concerned about messages like:

  [    4.487246] BIOS EDD facility v0.16 2004-Jun-25, 0 devices found
  [    4.487251] EDD information not available.

While these are more or less irrelevant, tell edd.c to not annoy anyone.

Signed-off-by: Johannes Thumshirn <jthumshirn@suse.de>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>