nvme-fc: unmap cmd_iu DMA on rsp_iu mapping failure in init_request

In the Linux kernel, the following vulnerability has been resolved: nvme-fc: unmap cmd_iu DMA on rsp_iu mapping failure in init_request __nvme_fc_init_request() maps cmd_iu and then rsp_iu for DMA. If the rsp_iu mapping fails, the original code only recorded the error and fell through: it left the already-mapped cmd_iu unmapped and still marked the op as FCPOP_STATE_IDLE before returning. Since blk-mq does not call .exit_request() when .init_request() fails, the cmd_iu mapping is leaked for every op whose rsp_iu mapping fails. Jump to an error path on rsp_iu mapping failure that unmaps cmd_iu and returns the error without marking the op idle, so it stays in the FCPOP_STATE_UNINIT state set by the initial memset().