drivers: usb: stm32: Limit the amount of bytes to write
drivers: usb: stm32: Limit the amount of bytes to write

Limit the amount of bytes to write to EP0 to 64 bytes so that there is
no overflow or error when sending.

Signed-off-by: Carles Cufi <853081dc8dca4fe6a7e3c984752718b5db36e060@nordicsemi.no>

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