RDMA/hns: Fix -Wframe-larger-than issue

RDMA/hns: Fix -Wframe-larger-than issue

Fix -Wframe-larger-than issue by allocating memory for qpc struct
with kzalloc() instead of using stack memory.

Fixes: 606bf89e98ef ("RDMA/hns: Refactor for hns_roce_v2_modify_qp function")
Reported-by: kernel test robot <lkp@intel.com>
Closes: https://lore.kernel.org/oe-kbuild-all/202506240032.CSgIyFct-lkp@intel.com/
Signed-off-by: Junxian Huang <huangjunxian6@hisilicon.com>
Link: https://patch.msgid.link/20250703113905.3597124-7-huangjunxian6@hisilicon.com
Signed-off-by: Leon Romanovsky <leon@kernel.org>