cxlflash: drop unlikely before IS_ERR_OR_NULL

IS_ERR_OR_NULL already contain an unlikely compiler flag. Drop it.

Signed-off-by: Geliang Tang <geliangtang@163.com>
Acked-by: Manoj Kumar <manoj@linux.vnet.ibm.com>
Acked-by: Matthew R. Ochs <mrochs@linux.vnet.ibm.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>