scsi: ufs: make ufshcd_config_pwr_mode of non-static func

This makes ufshcd_config_pwr_mode non-static so that other vendors like
exynos can use it.

Signed-off-by: Seungwon Jeon <essuuj@gmail.com>
Signed-off-by: Alim Akhtar <alim.akhtar@samsung.com>
Reviewed-by: Avri Altman <avri.altman@wdc.com>
Reviewed-by: Subhash Jadavani <subhashj@codeaurora.org>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>