scsi: csiostor: Fix dereference of null pointer rn

In the Linux kernel, the following vulnerability has been resolved: scsi: csiostor: Fix dereference of null pointer rn The error exit path when rn is NULL ends up deferencing the null pointer rn via the use of the macro CSIO_INC_STATS. Fix this by adding a new error return path label after the use of the macro to avoid the deference.