set flash sector count to 1024 for EFM32GG11_STK3701(MX25R3235F) set flash sector count to 2048 for NRF52840_DK(MX25R6435F)
- code refactoring and preparation for enabling DPI/QPI tests - reduced multiple test count to 4 - use common flash config header for all MX25RXX35F chips - fix sector erase max time on N25Q128A
* For EFM32GG11, since that is the only Silicon Labs target with QSPI per today * Verified working using the on-board flash and tests-mbed_hal-qspi