bt: Fix persisting appearance for le only device

When using le_scanning_manager the device appearance from advertising
data was not propagated to device's properties as a Class of Device.
This resulted in le-only earbud to contain no information about device
class which resulted in the icon in Bluetooth Settings menu to change
when dual-mode device was disconnected from the phone and the only
remaining device in the set was the le-only one.

Bug: 269067986
Test: manual: pair earbuds, disconnect dual-mode earbud, observe icon in
settings
Tag: #feature

Change-Id: Iee7d01afc3237b6deaa89d78e41f809ee790b87d