scsi: ufs: Reduce power management code duplication

scsi: ufs: Reduce power management code duplication

Move the dev_get_drvdata() calls into the ufshcd_{system,runtime}_*()
functions. Remove ufshcd_runtime_idle() since it is empty. This patch does
not change any functionality.

Link: https://lore.kernel.org/r/20210722033439.26550-3-bvanassche@acm.org
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Stanley Chu <stanley.chu@mediatek.com>
Cc: Can Guo <cang@codeaurora.org>
Cc: Asutosh Das <asutoshd@codeaurora.org>
Reviewed-by: Avri Altman <avri.altman@wdc.com>
Reviewed-by: Bean Huo <beanhuo@micron.com>
Reviewed-by: Daejun Park <daejun7.park@samsung.com>
Reviewed-by: Stanley Chu <stanley.chu@mediatek.com>
Signed-off-by: Bart Van Assche <bvanassche@acm.org>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>