UPSTREAM: util/cbfstool/lz4frame.c: Add comment to fall through

GCC7 has a new feature called -Wimplicit-fallthrough enabled by
default which checks for fallthrough in switch statements which is a
common error. When a fallthrough is actually intended a comment saying
so will satisfy GCC.

Fixes cbfstool not building with GCC7.

BUG=none
BRANCH=none
TEST=none

Change-Id: Ieb0affec0b5ea2c651469f92d5c15bf57cdc6cf8
Signed-off-by: Patrick Georgi <pgeorgi@google.com>
Original-Commit-Id: 54fd92bc34
Original-Change-Id: I83252fc96be7ce0971d4251b0fc88fbbd7440e71
Original-Signed-off-by: Arthur Heymans <arthur@aheymans.xyz>
Original-Reviewed-on: https://review.coreboot.org/20036
Original-Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Original-Reviewed-by: Nico Huber <nico.h@gmx.de>
Original-Reviewed-by: Paul Menzel <paulepanter@users.sourceforge.net>
Reviewed-on: https://chromium-review.googlesource.com/528190
Commit-Ready: Patrick Georgi <pgeorgi@chromium.org>
Tested-by: Patrick Georgi <pgeorgi@chromium.org>
Reviewed-by: Patrick Georgi <pgeorgi@chromium.org>

util/cbfstool/lz4/lib/lz4frame.c

@@ -1091,7 +1091,7 @@ size_t LZ4F_decompress(LZ4F_decompressionContext_t decompressionContext,
                 dctxPtr->tmpInTarget = minFHSize;   /* minimum to attempt decode */
                 dctxPtr->dStage = dstage_storeHeader;
             }
-
+	    /* Falls through. */
         case dstage_storeHeader:
             {
                 size_t sizeToCopy = dctxPtr->tmpInTarget - dctxPtr->tmpInSize;