mtd: ubi: annotate fallthrough

The UBI code uses an implicit switch/case fallthrough when handling two
related cases of bad header errors. Also there is a switch/case for unit
prefix handling (G/M/K), which accumulates multiplications.

Add our "fallthrough;" statement-like macro before the respective labels
in both cases, to avoid a warning when GCC's -Wimplicit-fallthrough
warning option is enabled.

Signed-off-by: Andre Przywara <andre.przywara@arm.com>
Reviewed-by: Heiko Schocher <hs@denx.de>
diff --git a/drivers/mtd/ubi/attach.c b/drivers/mtd/ubi/attach.c
index 2ef8fde..306da50 100644
--- a/drivers/mtd/ubi/attach.c
+++ b/drivers/mtd/ubi/attach.c
@@ -934,6 +934,7 @@
 			 * be a result of power cut during erasure.
 			 */
 			ai->maybe_bad_peb_count += 1;
+		fallthrough;
 	case UBI_IO_BAD_HDR:
 		if (ec_err)
 			/*
diff --git a/drivers/mtd/ubi/build.c b/drivers/mtd/ubi/build.c
index 1045377..50e4392 100644
--- a/drivers/mtd/ubi/build.c
+++ b/drivers/mtd/ubi/build.c
@@ -1400,12 +1400,15 @@
 	switch (*endp) {
 	case 'G':
 		result *= 1024;
+		fallthrough;
 	case 'M':
 		result *= 1024;
+		fallthrough;
 	case 'K':
 		result *= 1024;
 		if (endp[1] == 'i' && endp[2] == 'B')
 			endp += 2;
+		fallthrough;
 	case '\0':
 		break;
 	default: