RDMA/core: Fix ib_qp_usecnt_dec() called when error

RDMA/core: Fix ib_qp_usecnt_dec() called when error

ib_destroy_qp() would called by ib_create_qp_user() if error, the former
contains ib_qp_usecnt_dec(), but ib_qp_usecnt_inc() was not called before.

So move ib_qp_usecnt_inc() into create_qp().

Fixes: 6ef056b7f15b ("RDMA/core: Create clean QP creations interface for uverbs")
Link: https://lore.kernel.org/r/20220303024232.2847388-1-yajun.deng@linux.dev
Signed-off-by: Yajun Deng <yajun.deng@linux.dev>
Reviewed-by: Leon Romanovsky <leonro@nvidia.com>
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>