ARM: OMAP: DRA7: powerdomain data: Remove unused pwrsts_logic_ret

As per the latest revision F of public TRM for DRA7/AM57xx SoCs
SPRUHZ6F[1] (April 2016), with the exception of MPU power domain (and
CPUx sub power domains), all other power domains can either operate
in "ON" mode OR in some cases, "OFF" mode. For these power states,
the logic retention state is basically ignored by PRCM and does not
require to be programmed.

[1] http://www.ti.com/lit/pdf/spruhz6

Signed-off-by: Nishanth Menon <nm@ti.com>
Signed-off-by: Tony Lindgren <tony@atomide.com>