### What this PR does / why we need it?
func `get_kv_cache_spec` in model_runner changed a lot and caused error
in cpuoffloading connector which is copied from model_runner, this PR
adapts to new implemented `get_kv_cache_spec` to fix it.
### How was this patch tested?
- vLLM version: v0.11.0
- vLLM main:
2918c1b49c
Signed-off-by: lidenghui <lidenghui1110@gmail.com>