Bluetooth: controller: Fix PHY update proc symmetric rsp

Fix PHY update procedure to correctly handle master
requesting asymmetrical and slave symmetrical.

Fixes BT LL TS 5.1.0 conformance test:
LL/CON/MAS/BV-117-C [PHY Update Procedure - Master
Requests Asymmetrical, Slave Symmetrical]

Signed-off-by: Vinayak Kariappa Chettimada <vich@nordicsemi.no>