Fix events-queue failure on low CPU frequency
Fix events-queue failure on low CPU frequency

kjbracey-arm/mbed,mbedmicro/mbed,kjbracey-arm/mbed,mbedmicro/mbed,mbedmicro/mbed,kjbracey-arm/mbed,mbedmicro/mbed,kjbracey-arm/mbed,mbedmicro/mbed