scsi: ufs: Introduce ufshcd_is_auto_hibern8_supported()

The checking of Auto-Hibernation support is used in many places in the
driver, thus re-factor it as ufshcd_is_auto_hibern8_supported() to make
code more clean.

Signed-off-by: Stanley Chu <stanley.chu@mediatek.com>
Reviewed-by: Bean Huo <beanhuo@micron.com>
Reviewed-by: Alim Akhtar <alim.akhtar@samsung.com>
Reviewed-by: Avri Altman <Avri.Altman@wdc.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>