lib/zlib_inflate/inflate.c: remove fall through warnings

This patch remove all following fall through warnings by
adding /* fall through */ markers.
Note that we cannot add "__attribute__ ((fallthrough));" due to it is GCC7 only
arch/arm/boot/compressed/../../../../lib/zlib_inflate/inflate.c:384:25: warning: this statement may fall through [-Wimplicit-fallthrough=]
arch/arm/boot/compressed/../../../../lib/zlib_inflate/inflate.c:391:25: warning: this statement may fall through [-Wimplicit-fallthrough=]
arch/arm/boot/compressed/../../../../lib/zlib_inflate/inflate.c:393:16: warning: this statement may fall through [-Wimplicit-fallthrough=]
arch/arm/boot/compressed/../../../../lib/zlib_inflate/inflate.c:430:25: warning: this statement may fall through [-Wimplicit-fallthrough=]
arch/arm/boot/compressed/../../../../lib/zlib_inflate/inflate.c:556:25: warning: this statement may fall through [-Wimplicit-fallthrough=]
arch/arm/boot/compressed/../../../../lib/zlib_inflate/inflate.c:595:25: warning: this statement may fall through [-Wimplicit-fallthrough=]
arch/arm/boot/compressed/../../../../lib/zlib_inflate/inflate.c:602:25: warning: this statement may fall through [-Wimplicit-fallthrough=]
arch/arm/boot/compressed/../../../../lib/zlib_inflate/inflate.c:627:25: warning: this statement may fall through [-Wimplicit-fallthrough=]
arch/arm/boot/compressed/../../../../lib/zlib_inflate/inflate.c:646:25: warning: this statement may fall through [-Wimplicit-fallthrough=]
arch/arm/boot/compressed/../../../../lib/zlib_inflate/inflate.c:696:25: warning: this statement may fall through [-Wimplicit-fallthrough=]

It is easy to see that thoses fall through are needed since in each case state->mode are set to the case value just below.

Link: http://lkml.kernel.org/r/1536215920-19955-1-git-send-email-clabbe@baylibre.com
Signed-off-by: Corentin Labbe <clabbe@baylibre.com>
Cc: David Miller <davem@davemloft.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>