Bluetooth: controller: llcp: fix failing LL/CON/CEN/BV-55-C

The mandatory minimum PDU length conformance test was failing
because the LLCP did update the effective rx/tx times (and
corresponding notification to host).
This was due to a missing test condition.

This PR adds the missing conditions.

Note that with this change the refactored controller code is
similar to the legacy code; relevant code is in ull_conn.c,
in the function event_phy_upd_ind_prep

Signed-off-by: Andries Kruithof <andries.kruithof@nordicsemi.no>