hostapd: consistent reference counting for registry

hostapd: consistent reference counting for registry

Since `wpa_ucode_registry_add` collects its own reference to the values added, the
two functions `hostapd_ucode_bss_get_uval` and `hostapd_ucode_iface_get_uval` would
sometimes return a referenced object (from `uc_resource_new`) and sometimes return
an unreferenced object (from `wpa_ucode_registry_get`). Now, both functions always
return a referenced object.

This change also indirectly fixes `hostapd_ucode_bss_get_uval`, ensuring it now
always returns a referenced object.

Signed-off-by: Matthew Cather <mattbob4@gmail.com>
Signed-off-by: Felix Fietkau <nbd@nbd.name>