drivers/can/can.c: fix broken O_NONBLOCK

O_NONBLOCK open mode was broken since
#17360

MIN() comapres signed value (int) with unsigned value (size_t) which causes
an unexpected return value when ret is negative

Signed-off-by: raiden00pl <[email protected]>

Author: raiden00pl

drivers/can/can.c

@@ -518,7 +518,7 @@ static ssize_t can_read(FAR struct file *filep, FAR char *buffer,
 
   /* ret can be more than buflen due to roundup, so return at most buflen */
 
-  return ret ? MIN(ret, buflen) : -EMSGSIZE;
+  return ret ? MIN(ret, (int)buflen) : -EMSGSIZE;
 }
 
 /****************************************************************************