scsi: ufs: sysfs: Add sysfs entries for write booster

Adds unit, device, geometry descriptor sysfs entries.  Adds flags sysfs
entries for write booster.

Link: https://lore.kernel.org/r/98987ef17844292bd42c57613990a3a26c6de2b8.1587591527.git.asutoshd@codeaurora.org


Reviewed-by: Avri Altman <avri.altman@wdc.com>
Signed-off-by: Asutosh Das <asutoshd@codeaurora.org>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>