bus: ti-sysc: Add support for PRUSS SYSC type

bus: ti-sysc: Add support for PRUSS SYSC type

The PRU-ICSS present on AM33xx/AM43xx/AM57xx has a very unique
SYSCFG register. The register follows the OMAP4-style SYSC_TYPE3
for Master Standby and Slave Idle, but also has two additional
unique fields - STANDBY_INIT and SUB_MWAIT. The STANDBY_INIT is
a control bit that is used to initiate a Standby sequence (when
set) and trigger a MStandby request to the SoC's PRCM module. This
same bit is also used to enable the OCP master ports (when cleared)
to allow the PRU cores to access any peripherals or memory beyond
the PRU subsystem. The SUB_MWAIT is a ready status field for the
external access.

Add support for this SYSC type. The STANDBY_INIT has to be set
during suspend, without which it results in a hang in the resume
sequence on AM33xx/AM43xx boards and requires a board reset to
come out of the hang. Any PRU applications requiring external
access are supposed to clear the STANDBY_INIT bit. Note that
the PRUSS context is lost during a suspend sequence because the
PRUSS module is reset and/or disabled.

Signed-off-by: Suman Anna <s-anna@ti.com>
Signed-off-by: Roger Quadros <rogerq@ti.com>
[tony@atomide.com: updated quirk define number and to use -ENODEV]
Signed-off-by: Tony Lindgren <tony@atomide.com>