RDMA/cxgb4: free STAG index when TPT entry write fails

In the Linux kernel, the following vulnerability has been resolved: RDMA/cxgb4: free STAG index when TPT entry write fails write_tpt_entry() allocates a new STAG index with c4iw_get_resource() and bumps stats.stag.cur before programming the entry. When write_adapter_mem() fails, it returns the error without releasing the index or reversing the statistic. No MR is inserted into rhp->mrs, so deregistration never reclaims it, leaking the index until device teardown. Record whether this call allocated the index and, on a failed write, return it to tpt_table and decrement stats.stag.cur. Key the rollback on both the write error and that flag, not the error alone: a non-reset update carries a caller-owned STAG that this call did not allocate and must not free.