hash: add switch fall-through comments for arm64
hash: add switch fall-through comments for arm64

This fixes compiler warnings with GCC 7 for arm64 build.
Fixes: da8dcc27f644 ("hash: use armv8-a CRC32 instructions")

Signed-off-by: Jerin Jacob <5bca7d2a432bc0f5422b70b2701a4e4fa32edd00@caviumnetworks.com>

john-mcnamara-intel/dpdk,john-mcnamara-intel/dpdk,john-mcnamara-intel/dpdk,john-mcnamara-intel/dpdk