feat: fixed some bugs for running on real hardware

kernel/fs/fat.c

@@ -123,6 +123,11 @@ void print_chars(char *chars, int amount) {
 uint8_t fat_check_device(const block_device *device, uint8_t *first_sector) {
     fat_bpb bpb;
     memcpy((uint8_t *) &bpb, first_sector, sizeof(fat_bpb));
+    if (bpb.bpb.sectors_per_fat == 0 || bpb.bpb.sectors_per_cluster == 0) {
+        printf("Definitely not FAT\n");
+        return BLOCK_DEV_DRIVER_CHECK_NO_MATCH;
+    }
+
     printf("OEM: ");
     print_chars(bpb.bpb.oem_identifier, 11);
     printf("\n");