scsi: lpfc: Fix a possible null pointer dereference

In the Linux kernel, the following vulnerability has been resolved: scsi: lpfc: Fix a possible null pointer dereference In function lpfc_xcvr_data_show, the memory allocation with kmalloc might fail, thereby making rdp_context a null pointer. In the following context and functions that use this pointer, there are dereferencing operations, leading to null pointer dereference. To fix this issue, a null pointer check should be added. If it is null, use scnprintf to notify the user and return len.