CVE-2021-47198 scsi: lpfc: Fix use-after-free in lpfc_unreg_rpi() routine

In the Linux kernel, the following vulnerability has been resolved:

scsi: lpfc: Fix use-after-free in lpfc_unreg_rpi() routine

An error is detected with the following report when unloading the driver:
“KASAN: use-after-free in lpfc_unreg_rpi+0x1b1b”

The NLP_REG_LOGIN_SEND nlp_flag is set in lpfc_reg_fab_ctrl_node(), but the
flag is not cleared upon completion of the login.

This allows a second call to lpfc_unreg_rpi() to proceed with nlp_rpi set
to LPFC_RPI_ALLOW_ERROR. This results in a use after free access when used
as an rpi_ids array index.

Fix by clearing the NLP_REG_LOGIN_SEND nlp_flag in
lpfc_mbx_cmpl_fc_reg_login().