Fix several -Wno-implicit-fallthrough warnings

GCC is picky about the comment being where the break should go.

Change-Id: I05db2fb34025fefe2c6ddd1274c8e45b7cc5a4b6
Signed-off-by: Richard Hughes <richard@hughsie.com>
Reviewed-on: https://review.coreboot.org/c/30406
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Nico Huber <nico.h@gmx.de>
Reviewed-by: Paul Menzel <paulepanter@users.sourceforge.net>
Reviewed-by: Angel Pons <th3fanbus@gmail.com>
diff --git a/sb600spi.c b/sb600spi.c
index 1e2e5d5..1efb2ce 100644
--- a/sb600spi.c
+++ b/sb600spi.c
@@ -638,6 +638,7 @@
 	switch (amd_gen) {
 	case CHIPSET_SB7XX:
 		msg_pdbg(", DropOneClkOnRd/SpiClkGate=%i", (tmp >> 28) & 0x1);
+		/* Fall through. */
 	case CHIPSET_SB89XX:
 	case CHIPSET_HUDSON234:
 	case CHIPSET_YANGTZE: