drivers: usb_dc_sam: validate pointer in usb_dc_ep_is_stalled
drivers: usb_dc_sam: validate pointer in usb_dc_ep_is_stalled

Validate pointer argument in usb_dc_ep_is_stalled.

Fixes: #18824

Signed-off-by: Johann Fischer <b39b26e1812eb092eb217277792f3735321fa456@phytec.de>

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