Bugfix: Remove f16_kv, add offload_kqv field (#1019)

F16_KV appears to have been removed here: https://github.com/ggerganov/llama.cpp/pull/4312/commits/af99c6fbfc815df7dad94d8c1f20d55927b2203a

This addresses two issues:

 - #995 which just requests to add the KV cache offloading param
 - #1006 a NULL ptr exception when using the embeddings (introduced by
   leaving f16_kv in the fields struct)