scsi: ufs: core: Add lu_enable sysfs node

We need to check whether HPB is enabled on a given LU from the userspace
tool. Add lu_enable sysfs node.

Link: https://lore.kernel.org/r/20210804182128.458356-3-huobean@gmail.com


Tested-by: Avri Altman <avri.altman@wdc.com>
Reviewed-by: Avri Altman <avri.altman@wdc.com>
Signed-off-by: Bean Huo <beanhuo@micron.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>