M2351: Refine gpio_irq_set(...) with inconsistent GPIO_EnableInt(...) implementations
M2351: Refine gpio_irq_set(...) with inconsistent GPIO_EnableInt(...) implementations

No logic change

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