According to UFS specification, there are two WriteBooster mode of
operations: "LU dedicated buffer" mode and "shared buffer" mode.  In the
"LU dedicated buffer" mode, the WriteBooster Buffer is dedicated to a
logical unit.

If the device supports the "LU dedicated buffer" mode, this mode is
configured by setting bWriteBoosterBufferType to 00h. The logical unit
WriteBooster Buffer size is configured by setting the
dLUNumWriteBoosterBufferAllocUnits field of the related Unit
Descriptor. Only a value greater than zero enables the WriteBooster feature
in the logical unit.

Modify ufshcd_wb_probe() as above description to support LU Dedicated
buffer mode.

Note that according to UFS 3.1 specification, the valid value of
bDeviceMaxWriteBoosterLUs parameter in Geometry Descriptor is 1, which
means at most one LUN can have WriteBooster buffer in "LU dedicated buffer
mode". Therefore this patch supports only one LUN with WriteBooster
enabled. All WriteBooster related sysfs nodes are specifically mapped to
the LUN with WriteBooster enabled in LU Dedicated buffer mode.

Link: https://lore.kernel.org/r/20200508080115.24233-7-stanley.chu@mediatek.comReviewed-by: Avri Altman <avri.altman@wdc.com>
Reviewed-by: Bean Huo <beanhuo@micron.com>
Reviewed-by: Asutosh Das <asutoshd@codeaurora.org>
Signed-off-by: Stanley Chu <stanley.chu@mediatek.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>