Mark switch cases where we are expecting to fall through.
Fix the following warning (Building: assabet_defconfig arm):
drivers/mtd/maps/sa1100-flash.c: In function ‘sa1100_probe_subdev’:
drivers/mtd/maps/sa1100-flash.c:82:3: warning: this statement may fall through [-Wimplicit-fallthrough=]
   printk(KERN_WARNING "SA1100 flash: unknown base address "
   ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
          "0x%08lx, assuming CS0\n", phys);
          ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
drivers/mtd/maps/sa1100-flash.c:85:2: note: here
  case SA1100_CS0_PHYS:
  ^~~~
Signed-off-by: Gustavo A. R. Silva <gustavo@embeddedor.com>
        default:
                printk(KERN_WARNING "SA1100 flash: unknown base address "
                       "0x%08lx, assuming CS0\n", phys);
+               /* Fall through */
 
        case SA1100_CS0_PHYS:
                subdev->map.bankwidth = (MSC0 & MSC_RBW) ? 2 : 4;