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 ...