scsi: sg: Avoid sg device teardown race

In the Linux kernel, the following vulnerability has been resolved: scsi: sg: Avoid sg device teardown race sg_remove_sfp_usercontext() must not use sg_device_destroy() after calling scsi_device_put(). sg_device_destroy() is accessing the parent scsi_device request_queue which will already be set to NULL when the preceding call to scsi_device_put() removed the last reference to the parent scsi_device. The resulting NULL pointer exception will then crash the kernel.