Bluetooth: HFP_AG: Update SDP discovery

Add set the parameter `type` to value
`BT_SDP_DISCOVER_SERVICE_SEARCH_ATTR`.

Update the SDP discovery callback function by adding a third parameter
`const struct bt_sdp_discover_params *params`. Make it align with
`bt_sdp_discover_func_t`.

Signed-off-by: Lyle Zhu <lyle.zhu@nxp.com>