ubi: Mark expected switch fall-throughs

In preparation to enabling -Wimplicit-fallthrough, mark switch cases
where we are expecting to fall through.

Addresses-Coverity-ID: 1373884 ("Missing break in switch")
Addresses-Coverity-ID: 114869 ("Missing break in switch")
Addresses-Coverity-ID: 114870 ("Missing break in switch")
Signed-off-by: Gustavo A. R. Silva <[e-mail]>
Signed-off-by: Richard Weinberger <[e-mail]>

drivers/mtd/ubi/attach.c

···
 			 * be a result of power cut during erasure.
 			 */
 			ai->maybe_bad_peb_count += 1;
+		/* fall through */
 	case UBI_IO_BAD_HDR:
 			/*
 			 * If we're facing a bad VID header we have to drop *all*

drivers/mtd/ubi/build.c

···
 	switch (*endp) {
 	case 'G':
 		result *= 1024;
+		/* fall through */
 	case 'M':
 		result *= 1024;
+		/* fall through */
 	case 'K':
 		result *= 1024;
 		if (endp[1] == 'i' && endp[2] == 'B')