scsi: megaraid_sas: Fix fw_crash_buffer_show()

If crash_dump_buf is not allocated then crash dump can't be available.
Replace logical 'and' with 'or'.

Signed-off-by: Tomas Henzl <thenzl@redhat.com>
Link: https://lore.kernel.org/r/20230324135249.9733-1-thenzl@redhat.com
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>