phy: cadence-torrent: Refactor code for reusability

Add a separate function to set different power state values.
Use uniform polling timeout value. Also check return values
of functions for proper error handling.

Signed-off-by: Swapnil Jakhade <sjakhade@cadence.com>
Signed-off-by: Yuti Amonkar <yamonkar@cadence.com>
Signed-off-by: Kishon Vijay Abraham I <kishon@ti.com>