ata: ahci: Drop low power policy board type

ata: ahci: Drop low power policy board type

The low power policy board type was introduced to allow systems
to get into deep states reliably.  Before it was introduced `min_power`
was causing problems for a number of drives.  New power policies
`min_power_with_partial` and `med_power_with_dipm` have been introduced
which provide a more stable baseline for systems.

Tested-by: Damien Le Moal <[email protected]>
Tested-by: Jian-Hong Pan <[email protected]>
Acked-by: Jian-Hong Pan <[email protected]>
Acked-by: Christoph Hellwig <[email protected]>
Reviewed-by: Damien Le Moal <[email protected]>
Reviewed-by: Mario Limonciello <[email protected]>
Reviewed-by: Mika Westerberg <[email protected]>
Suggested-by: Christoph Hellwig <[email protected]>
Signed-off-by: Mario Limonciello <[email protected]>
[cassel: rebase patch and fix trivial conflicts]
Signed-off-by: Niklas Cassel <[email protected]>