scsi: ufs: core: Export hibern8 entry and exit functions

Qualcomm controllers need to be in hibern8 before scaling up or down the
clocks. Hence, export the hibern8 entry and exit functions.

Link: https://lore.kernel.org/r/a29bfdd0c8f1d1a3e5fb69e43ea277c97a7f0cb6.1632818942.git.nguyenb@codeaurora.org


Reviewed-by: Bart Van Assche <bvanassche@acm.org>
Reviewed-by: Alim Akhtar <alim.akhtar@samsung.com>
Signed-off-by: Asutosh Das <asutoshd@codeaurora.org>
Signed-off-by: Bao D. Nguyen <nguyenb@codeaurora.org>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>