hisi_qm_get_free_qp_num() is to get the free queue number on the function.
It is a simple function and is only called by
hisi_qm_get_available_instances().

This patch modifies to get the free queue directly in
hisi_qm_get_available_instances(), and remove hisi_qm_get_free_qp_num().
Signed-off-by: Weili Qian <qianweili@huawei.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>