[nrf fromtree] Bluetooth: Host: Fix overwriting ECC error value

Jump straight to the exit portion of the function in the case that
psa_destroy_key() failed and we set err to a non-zero value. This also
fixes Coverity CID 487701 "Code maintainability issues  (UNUSED_VALUE)".

Signed-off-by: Johan Hedberg <[email protected]>
(cherry picked from commit 8b356fd)

Author: jhedberg

subsys/bluetooth/host/ecc.c

@@ -220,6 +220,7 @@ static void generate_dh_key(struct k_work *work)
 	if (ret != PSA_SUCCESS) {
 		LOG_ERR("Failed to destroy the key %d", ret);
 		err = -EIO;
+		goto exit;
 	}
 
 	err = 0;