drivers/can/can.c: fix broken O_NONBLOCK

[raiden00pl]

Summary

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.

Impact

fix regression

Testing

simulator with CAN.

a simple test showing that the previous code was wrong:

#include <stdio.h>

int main()
{
#define MIN(a,b) (((a) < (b)) ? (a) : (b))
  int x = -11; size_t y = 11;
  printf("x=%d y=%d min=%d min=%d\n", x, y, MIN(x,y), MIN(x,(int)y));
  return 0;
}

x=-11 y=11 min=11 min=-11

[acassis]

Good catch!