UFSHCI_QUIRK_SKIP_MANUAL_WB_FLUSH_CTRL is intended to skip enabling
fWriteBoosterBufferFlushEn while WriteBooster is initializing.  Therefore
it is better to apply the checking during WriteBooster initialization only.

Link: https://lore.kernel.org/r/20201222072905.32221-3-stanley.chu@mediatek.comReviewed-by: Can Guo <cang@codeaurora.org>
Signed-off-by: Stanley Chu <stanley.chu@mediatek.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>