scsi: ufshcd-platform: remove the useless cast in ERR_PTR/IS_ERR

IS_ERR and ERR_PTR already forcefully cast their argument, hence there
is no need for additional (complex) casting.

Signed-off-by: Tomas Winkler <tomas.winkler@intel.com>
Reviewed-by: Subhash Jadavani <subhashj@codeaurora.org>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>