scsi: ufs: make ufshcd_is_{device_present, hba_active}() return bool

ufshcd driver generally uses bool for is_xxx type things instead of int,
so conform to its style.

Signed-off-by: Tomohiro Kusumi <tkusumi@tuxera.com>
Reviewed-by: Subhash Jadavani <subhashj@codeaurora.org>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>