samples: usb: mass: increase main stack size

"ZEPHYR FATAL ERROR 2: Stack overflow on CPU 0" observed on a few
supported platforms when using SD card disk. Increase main stack size
for next USB device stack configuration to prevent stack overflow.

Signed-off-by: Johann Fischer <[email protected]>

Author: jfischer-no

samples/subsys/usb/mass/usbd_next_prj.conf

@@ -12,4 +12,4 @@ CONFIG_UDC_DRIVER_LOG_LEVEL_WRN=y
 
 CONFIG_SAMPLE_USBD_PID=0x0008
 CONFIG_SAMPLE_USBD_PRODUCT="USBD MSC sample"
-CONFIG_MAIN_STACK_SIZE=1536
+CONFIG_MAIN_STACK_SIZE=2048