drivers: flash: nRF5x: Fix co-operation with Bluetooth controller
drivers: flash: nRF5x: Fix co-operation with Bluetooth controller

Fixed incorrect comparison of FLASH_SLOT in microseconds
with ticks elapsed.

This caused Bluetooth controller to try scheduling events
beyond the acceptable soft real-time design limits, due to
the CPU halted for flash erase operation.

Fixes #6229.

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

punitvara/zephyr,ldts/zephyr,Vudentz/zephyr,GiulianoFranchetto/zephyr,mbolivar/zephyr,explora26/zephyr,GiulianoFranchetto/zephyr,punitvara/zephyr,ldts/zephyr,GiulianoFranchetto/zephyr,galak/zephyr,galak/zephyr,explora26/zephyr,zephyriot/zephyr,zephyrproject-rtos/zephyr,mbolivar/zephyr,nashif/zephyr,Vudentz/zephyr,punitvara/zephyr,kraj/zephyr,explora26/zephyr,galak/zephyr,mbolivar/zephyr,zephyriot/zephyr,kraj/zephyr,zephyriot/zephyr,ldts/zephyr,Vudentz/zephyr,ldts/zephyr,galak/zephyr,Vudentz/zephyr,explora26/zephyr,finikorg/zephyr,zephyrproject-rtos/zephyr,GiulianoFranchetto/zephyr,punitvara/zephyr,mbolivar/zephyr,Vudentz/zephyr,finikorg/zephyr,mbolivar/zephyr,zephyrproject-rtos/zephyr,galak/zephyr,ldts/zephyr,zephyrproject-rtos/zephyr,finikorg/zephyr,kraj/zephyr,nashif/zephyr,finikorg/zephyr,finikorg/zephyr,zephyriot/zephyr,nashif/zephyr,zephyrproject-rtos/zephyr,punitvara/zephyr,zephyriot/zephyr,kraj/zephyr,Vudentz/zephyr,kraj/zephyr,GiulianoFranchetto/zephyr,nashif/zephyr,nashif/zephyr,explora26/zephyr