Bluetooth: Added missing checks for whether CONFIG_BT_PRIVACY is enabled

Fixes error encountered during connecting BLE endpoint.
[bt] [ERR] le_remote_feat_complete: Unable to lookup conn for handle 32

This is to work around a buggy controller that states support for
enhanced privacy, but misbehaves when it's enabled. This change
makes it possible to ensure the host doesn't try to enable the enhanced
event by simply disabling the privacy feature in Kconfig.

Signed-off-by: Vakul Garg <vakul.garg@nxp.com>