scsi: ufs: fix timeout waiting for doorbell clear

ufshcd_wait_for_doorbell_clr() function should wait for the
doorbell to be cleared until the specified timeout period but
current implementation really seems to be waiting until the doorbell
is cleared (instead of timing out after timeout period), this
change fixes this issue.

Change-Id: I0dee77db7d319250b5fab5f77e51175ea7d1d664
Signed-off-by: Subhash Jadavani <subhashj@codeaurora.org>