cxl/mbox: fix logical vs bitwise typo

This should be bitwise & instead of &&.

Fixes: 6179045c ("cxl/mbox: Block immediate mode in SET_PARTITION_INFO command")
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Link: https://lore.kernel.org/r/YmpgkbbQ1Yxu36uO@kili


Signed-off-by: Dan Williams <dan.j.williams@intel.com>