Bluetooth: audio: Fix PACS location chrc properties

If the characteristic is non-writtable, the BT_GATT_CHRC_WRITE property
flag shall be unset. Moreover, threre is no point to set
BT_GATT_PERM_WRITE_ENCRYPT permission flag as well if the attribute has
no `write` callback set anyway.

Signed-off-by: Mariusz Skamra <mariusz.skamra@codecoup.pl>