lpfc: Fix pointer checks and comments in LS receive refactoring

Additional testing encountered null pointers that weren't fully qualified
in lpfc_nvmet_xmt_ls_abort_cmp() and lpfc_nvmet_unsol_issue_abort().

The same error was detected and reported by static checker reporting:
  drivers/scsi/lpfc/lpfc_sli.c:2905 lpfc_nvme_unsol_ls_handler()
  error: we previously assumed 'phba->targetport' could be null
    (see line 2837)

Fix by making phba->nvmet_support and phba->targetport validity checks
in lpfc_nvmet_xmt_ls_abort_cmp() and lpfc_nvmet_unsol_issue_abort().

Fixes: 3a8070c5 (“lpfc: Refactor NVME LS receive handling”)
Reported-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Paul Ely <paul.ely@broadcom.com>
Signed-off-by: James Smart <jsmart2021@gmail.com>
Reviewed-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Christoph Hellwig <hch@lst.de>