Bluetooth: doc: Fix displacement of storage keys description

Improves placement of well known storage keys type values description
in Bluetooth API documentation by moving the comment to separate line
above the item it describes.

Change-Id: I6a9182d135983c5037cf44a4fda4305abfa4387f
Signed-off-by: Arkadiusz Lichwa <arkadiusz.lichwa@tieto.com>