UPSTREAM: scsi: ufs: Cleanup WriteBooster feature

Small cleanup as below items,

 1. Use ufshcd_is_wb_allowed() directly instead of ufshcd_wb_sup() since
    ufshcd_wb_sup() just returns the result of ufshcd_is_wb_allowed().

 2. In ufshcd_suspend(), "else if (!ufshcd_is_runtime_pm(pm_op)) can be
    simplified to "else" since both have the same meaning.

This patch does not change any functionality.

Link: https://lore.kernel.org/r/20200508080115.24233-9-stanley.chu@mediatek.com


Reviewed-by: Avri Altman <avri.altman@wdc.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>

Bug: 151050916
(cherry picked from commit 79e3520f82cb91e46e7db1af14ad916d6036dde8)
Change-Id: I7329575ba3ddce6976072c91570a71f1bbbbe92f
Signed-off-by: Stanley Chu <stanley.chu@mediatek.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@google.com>