[SCSI] ufs: reverse the ufshcd_is_device_present logic

Otherwise it counter intuitively returns 0 if device is present.

Signed-off-by: Venkatraman S <svenkatr@ti.com>
Reviewed-by: Namjae Jeon <linkinjeon@gmail.com>
Acked-by: Santosh Y <santoshsy@gmail.com>
Signed-off-by: James Bottomley <JBottomley@Parallels.com>