Bluetooth: controller: split: Fix PHY update tx pause
Bluetooth: controller: split: Fix PHY update tx pause

Data transmission was paused when PHY update request control
PDU was enqueued in ULL. If there was pending data PDU in
ULL that was not enqueued towards LLL, this caused
transmission to stall.

Move the tx pause due to PHY update request/response being
enqueued to pre_tx_ack callback, this way all pending PDUs
in ULL is enqueued to LLL.

Signed-off-by: Vinayak Kariappa Chettimada <e780c9f87dc729ad454f47292ad82c8652353064@nordicsemi.no>

nashif/zephyr,Vudentz/zephyr,finikorg/zephyr,galak/zephyr,zephyrproject-rtos/zephyr,nashif/zephyr,galak/zephyr,Vudentz/zephyr,galak/zephyr,finikorg/zephyr,zephyrproject-rtos/zephyr,Vudentz/zephyr,nashif/zephyr,Vudentz/zephyr,nashif/zephyr,Vudentz/zephyr,galak/zephyr,galak/zephyr,finikorg/zephyr,zephyrproject-rtos/zephyr,finikorg/zephyr,finikorg/zephyr,zephyrproject-rtos/zephyr,Vudentz/zephyr,zephyrproject-rtos/zephyr,nashif/zephyr