scsi: ufs: core: Fix the polling implementation

Fix the following issues in ufshcd_poll():

 - If polling succeeds, return a positive value.

 - Do not complete polling requests from interrupt context because the
   block layer expects these requests to be completed from thread
   context. From block/bio.c:

     If REQ_ALLOC_CACHE is set, the final put of the bio MUST be done from
     process context, not hard/soft IRQ.

Fixes: eaab9b57 ("scsi: ufs: Implement polling support")
Signed-off-by: Bart Van Assche <bvanassche@acm.org>
Link: https://lore.kernel.org/r/20221118233717.441298-1-bvanassche@acm.org


Reviewed-by: Adrian Hunter <adrian.hunter@intel.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>