drivers: usb: fix a buffer overflow in usb_sam0.c
drivers: usb: fix a buffer overflow in usb_sam0.c

The driver currently blindly copies all of the outgoing bytes into the
endpoint.  Instead, calculate the endpoint size and copy up to that
amount instead.

Signed-off-by: Michael Hope <c71d7810e3c04e4d6ad9df326b82536b86a1bfbc@google.com>

finikorg/zephyr,galak/zephyr,zephyrproject-rtos/zephyr,galak/zephyr,nashif/zephyr,finikorg/zephyr,Vudentz/zephyr,Vudentz/zephyr,Vudentz/zephyr,galak/zephyr,Vudentz/zephyr,nashif/zephyr,finikorg/zephyr,zephyrproject-rtos/zephyr,nashif/zephyr,finikorg/zephyr,zephyrproject-rtos/zephyr,nashif/zephyr,zephyrproject-rtos/zephyr,zephyrproject-rtos/zephyr,nashif/zephyr,Vudentz/zephyr,galak/zephyr,galak/zephyr,finikorg/zephyr,Vudentz/zephyr