ARM: OMAP2+: Powerdomain: Remove the need to always have a voltdm associated to a...

ARM: OMAP2+: Powerdomain: Remove the need to always have a voltdm associated to a pwrdm

The powerdomain framework currently expects all powerdomains to be associated with
a corresponding voltagedomain. For some SoCs' (like the already existing AM33xx
family, or for the upcoming AM437x and DRA7 SoCs') which
do not have a Voltage controller/Voltage Processor (neither the SR I2C
bus to communicate with the PMIC) there is no need for a Powerdomain to have
a voltage domain association since there is no auto-scaling of voltages possible
using the voltage FSM.

Extend the arch operations to add an api which the powerdomain core can
then use to identify if a voltdm lookup and association for a powerdomain
is really needed.

Acked-by: Nishanth Menon <[email protected]>
Acked-by: Vaibhav Hiremath <[email protected]>
Signed-off-by: Rajendra Nayak <[email protected]>
Acked-by: Santosh Shilimkar <[email protected]>
Tested-by: Afzal Mohammed <[email protected]> # am335x evm
Signed-off-by: Kevin Hilman <[email protected]>